Name: long-term continuous measurement of renal blood flow in conscious rats
Uploaded: 2022-02-08T15:00:00
Description: Watch this Scientific Journal Video about Long-Term Continuous Measurement of Renal Blood Flow in Conscious Rats at JoVE.com

This study was supported by grants for scientific research (P01 HL116264, RO1 HL137748). The authors would like to thank Theresa Kurth for her advice and help in maintaining the experimental environment as the lab manager.

The protocol is approved by the Medical College of Wisconsin Institutional Animal Care and Use. Dahl salt-sensitive rats (males and females), ~8 weeks of age, 200-350 g, were used for the experiments.
1. Animal preparation
<ol>
	<li>Install a movement response caging system for the rat, a perivascular flow module, syringe pump, recording device, and software (see Table of Materials) in the animal room.</li>
	<li>Place the rats in the cage to become familiar ...

<ol>
	<li>Chonchol, M., Smogorzewski, M., Stubbs, J., Yu, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Brenner &amp; Rector's The Kidney. 11, (2019).</li><li>Chen, J. -. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phosphatidylinositol+3-kinase+signaling+determines+kidney+size.">Phosphatidylinositol 3-kinase signaling determines kidney size.</a> Journal of Clinical Investigation. 125 (6), 2429-2444 (2015).</li><li>Sigmon, D. H., Gonzalez-Feldman, E., Cavasin, M. A., Potter, D. L., Beierwaltes, W. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+nitric+oxide+in+the+renal+hemodynamic+response+to+unilateral+nephrectomy.">Role of nitric oxide in the renal hemodynamic response to unilateral nephrectomy.</a> Journal of the American Society of Nephrology. 15 (6), 1413-1420 (2004).</li><li>Romero, C. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Noninvasive+measurement+of+renal+blood+flow+by+magnetic+resonance+imaging+in+rats.">Noninvasive measurement of renal blood flow by magnetic resonance imaging in rats.</a> American Journal of Physiology-Renal Physiology. 314 (1), 99-106 (2018).</li><li>Basile, D. P., Anderson, M. D., Sutton, T. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathophysiology+of+acute+kidney+injury.">Pathophysiology of acute kidney injury.</a> Comprehensive Physiology. 2 (2), 1303-1353 (2012).</li><li>Regan, M. C., Young, L. S., Geraghty, J., Fitzpatrick, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regional+renal+blood+flow+in+normal+and+disease+states.">Regional renal blood flow in normal and disease states.</a> Urological Research. 23 (1), 1-10 (1995).</li><li>Ter Wee, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+calcium+antagonists+on+renal+hemodynamics+and+progression+of+nondiabetic+chronic+renal+disease.">Effects of calcium antagonists on renal hemodynamics and progression of nondiabetic chronic renal disease.</a> Archives of Internal Medicine. 154 (11), 1185 (1994).</li><li>Mazze, R. I., Cousins, M. J., Barr, G. 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L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+glomerular+filtration+rate+and+effective+renal+plasma+flow+in+the+conscious+beagle+dog+by+single+intravenous+bolus+of+iohexol+and+p-aminohippuric+acid.">Measurement of glomerular filtration rate and effective renal plasma flow in the conscious beagle dog by single intravenous bolus of iohexol and p-aminohippuric acid.</a> Journal of Pharmacological and Toxicological Methods. 41 (1), 17-25 (1999).</li><li>Wei, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantification+of+renal+blood+flow+with+contrast-enhanced+ultrasound.">Quantification of renal blood flow with contrast-enhanced ultrasound.</a> Journal of the American College of Cardiology. 37 (4), 1135-1140 (2001).</li><li>Cao, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Contrast-enhanced+ultrasound+for+assessing+renal+perfusion+impairment+and+predicting+acute+kidney+injury+to+chronic+kidney+disease+progression.">Contrast-enhanced ultrasound for assessing renal perfusion impairment and predicting acute kidney injury to chronic kidney disease progression.</a> Antioxidants &amp; Redox Signaling. 27 (17), 1397-1411 (2017).</li><li>Markl, M., Frydrychowicz, A., Kozerke, S., Hope, M., Wieben, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=4D+flow+MRI.">4D flow MRI.</a> Journal of Magnetic Resonance Imaging. 36 (5), 1015-1036 (2012).</li><li>Juillard, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+renal+blood+flow+measurement+by+positron+emission+tomography+in+patients+with+CRF.">Dynamic renal blood flow measurement by positron emission tomography in patients with CRF.</a> American Journal of Kidney Diseases. 40 (5), 947-954 (2002).</li><li>Ju&#225;rez-Orozco, L. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+of+cardiac+and+renal+perfusion+in+a+rat+model+with+13N-NH3+micro-PET.">Imaging of cardiac and renal perfusion in a rat model with 13N-NH3 micro-PET.</a> The International Journal of Cardiovascular Imaging. 31 (1), 213-219 (2015).</li><li>Mori, T., Cowley, A. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+pressure+in+angiotensin+II-induced+renal+injury.">Role of pressure in angiotensin II-induced renal injury.</a> Hypertension. 43 (4), 752-759 (2004).</li><li>Mori, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+perfusion+pressure+accelerates+renal+injury+in+salt-sensitive+hypertension.">High perfusion pressure accelerates renal injury in salt-sensitive hypertension.</a> Journal of the American Society of Nephrology. 19 (8), 1472-1482 (2008).</li><li>Polichnowski, A. J., Cowley, A. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pressure-induced+renal+injury+in+angiotensin+II+versus+norepinephrine-induced+hypertensive+rats.">Pressure-induced renal injury in angiotensin II versus norepinephrine-induced hypertensive rats.</a> Hypertension. 54 (6), 1269-1277 (2009).</li><li>Polichnowski, A. J., Jin, C., Yang, C., Cowley, A. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+renal+perfusion+pressure+versus+angiotensin+II+renal+oxidative+stress+in+angiotensin+II-induced+hypertensive+rats.">Role of renal perfusion pressure versus angiotensin II renal oxidative stress in angiotensin II-induced hypertensive rats.</a> Hypertension. 55 (6), 1425-1430 (2010).</li><li>Evans, L. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increased+perfusion+pressure+drives+renal+T-cell+infiltration+in+the+dahl+salt-sensitive+rat.">Increased perfusion pressure drives renal T-cell infiltration in the dahl salt-sensitive rat.</a> Hypertension. 70 (3), 543-551 (2017).</li><li>Shimada, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Renal+perfusion+pressure+determines+infiltration+of+leukocytes+in+the+kidney+of+rats+with+angiotensin+II-induced+hypertension.">Renal perfusion pressure determines infiltration of leukocytes in the kidney of rats with angiotensin II-induced hypertension.</a> Hypertension. 76 (3), 849-858 (2020).</li><li>Cousins, M. J., Mazze, R. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anaesthesia,+surgery+and+renal+function:+Immediate+and+delayed+effects.">Anaesthesia, surgery and renal function: Immediate and delayed effects.</a> Anaesthesia and Intensive Care. 1 (5), 355-373 (1973).</li><li>Cousins, M. J., Skowronski, G., Plummer, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anaesthesia+and+the+kidney.">Anaesthesia and the kidney.</a> Anaesthesia and Intensive Care. 11 (4), 292-320 (1983).</li><li>Schiffer, T. A., Christensen, M., Gustafsson, H., Palm, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+inactin+on+kidney+mitochondrial+function+and+production+of+reactive+oxygen+species.">The effect of inactin on kidney mitochondrial function and production of reactive oxygen species.</a> PLOS ONE. 13 (11), 0207728 (2018).</li><li>Evans, R. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chronic+renal+blood+flow+measurement+in+dogs+by+transit-time+ultrasound+flowmetry.">Chronic renal blood flow measurement in dogs by transit-time ultrasound flowmetry.</a> Journal of Pharmacological and Toxicological Methods. 38 (1), 33-39 (1997).</li><li>Bell, T. D., DiBona, G. F., Biemiller, R., Brands, M. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Continuously+measured+renal+blood+flow+does+not+increase+in+diabetes+if+nitric+oxide+synthesis+is+blocked.">Continuously measured renal blood flow does not increase in diabetes if nitric oxide synthesis is blocked.</a> American Journal of Physiology-Renal Physiology. 295 (5), 1449-1456 (2008).</li></ol>

The present protocol describes a technique that utilizes commercially available instrumentation to record RBF and arterial pressure continuously over many weeks. In addition, urine can be collected using the device described in step 1.1. It can also be used to evaluate metabolites in the urine and, when an arterial catheter is implanted, blood sampling for analysis.
Traditionally, RBF measurements have been obtained acutely in surgically prepared anesthetized animals or estimated by PAH cleara...

The kidneys are only 0.5% of the bodyweight but rich in blood flow, receiving 20%-25% of the total cardiac output1. The regulation of renal blood flow (RBF) is central to kidney function, body fluid, and electrolyte homeostasis. The importance of blood flow regulation to the kidney is nicely illustrated by the substantial increase of RBF in the remaining kidney after unilateral nephrectomy2,3,4 and by the reductions of RBF that occur in kidney failure5,6,7. Whether such changes in RBF occur in response to alterations in kidney function or a decrease in function due to reduction of RBF has been challenging to ascertain in anesthetized surgically prepared animals or human subjects. Temporal studies are required in which the events can be determined before and following a defined change and observed in the same animal during the progression of events. In the animal and human studies, RBF has been estimated indirectly by the clearance of para-amino hippuric acid (PAH)8,9,10 and in more recent time by imaging techniques such as ultrasound9,11,12, MRI4,13, and PET-CT14,15 which give helpful snapshot images of each kidney and which can follow the progression of the disease. It is challenging to evaluate RBF in small animals by ultrasound or MRI scans without anesthesia. It has been impossible to continuously measure RBF under conscious conditions in the same rat over prolonged periods.
The present protocol, therefore, developed techniques that enable simultaneous continuous 24 h/day measurements of RBF, which has been combined with continuous blood pressure measurement methods for freely moving rats as described previously16,17,18,19,20,21. This technology allows for the temporal evaluation of RBF in various models of rats to study cause-effect relationships in various renal disorders in the future.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1RB probe</td>
			<td>Transonic</td>
			<td>1RB</td>
			<td>ultrasonic flow probe</td>
		</tr>
		<tr>
			<td>Betadine</td>
			<td>Avrio Health</td>
			<td></td>
			<td>povidone-iodine</td>
		</tr>
		<tr>
			<td>Buprenorphine SR-LAB</td>
			<td>ZooPharm</td>
			<td></td>
			<td>Buprenorphine</td>
		</tr>
		<tr>
			<td>Cefazolin</td>
			<td>APOTEX</td>
			<td>NDC 60505</td>
			<td>Cefazolin</td>
		</tr>
		<tr>
			<td>Crile Hemostats</td>
			<td>Fine Surgical Instruments</td>
			<td>13004-14</td>
			<td>Hemostats for blunt dissection</td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>Piramal</td>
			<td>NDC 66794</td>
			<td>Isoflurane</td>
		</tr>
		<tr>
			<td>Medium Clear PVC cement</td>
			<td>Oatey</td>
			<td></td>
			<td>PVC cement</td>
		</tr>
		<tr>
			<td>Mersilene polyester fiber mesh</td>
			<td>Ethicon</td>
			<td></td>
			<td>polyester fiber mesh</td>
		</tr>
		<tr>
			<td>MetriCide28</td>
			<td>Metrex</td>
			<td>SKU 10-2805</td>
			<td>2.5% glutaraldehyde</td>
		</tr>
		<tr>
			<td>Micro-Renathane 0.025 x 0.012</td>
			<td>Braintree Scientific</td>
			<td>MRE 025</td>
			<td>use for catheter</td>
		</tr>
		<tr>
			<td>MINI HYPE-WIPE</td>
			<td>Current Technologies</td>
			<td>#9803</td>
			<td>1% sodium hypochlorite</td>
		</tr>
		<tr>
			<td>Oatey Medium Clear PVC Cement</td>
			<td>Oatey</td>
			<td>#31018</td>
			<td>PVC cement</td>
		</tr>
		<tr>
			<td>PHD2000 syringe pump</td>
			<td>Harvard apparatus</td>
			<td>71-2000</td>
			<td>syringe pump</td>
		</tr>
		<tr>
			<td>Ponemah software</td>
			<td>DSI</td>
			<td></td>
			<td>recording software</td>
		</tr>
		<tr>
			<td>Precision 3630 Tower</td>
			<td>Dell</td>
			<td></td>
			<td>Computer for recording</td>
		</tr>
		<tr>
			<td>Raturn Stand-Alone System</td>
			<td>BASi</td>
			<td>MD-1407</td>
			<td>a movement response caging system</td>
		</tr>
		<tr>
			<td>RenaPulse High Fidelity Pressure Tubing 0.040 x 0.025</td>
			<td>Braintree Scientific</td>
			<td>RPT 040</td>
			<td>use for catheter</td>
		</tr>
		<tr>
			<td>Silicone cuff</td>
			<td>Transonic</td>
			<td>AAPC102</td>
			<td>skin button</td>
		</tr>
		<tr>
			<td>Surgical lubricant sterile bacteriostatic</td>
			<td>Fougera</td>
			<td>0168-0205-36</td>
			<td>gell for flow probe</td>
		</tr>
		<tr>
			<td>Tergazyme</td>
			<td>Alconox</td>
			<td></td>
			<td>protease contained anionic detergent</td>
		</tr>
		<tr>
			<td>TS420 Perivascular Flow Module</td>
			<td>Transonic</td>
			<td>TS420</td>
			<td>perivascular flow module</td>
		</tr>
		<tr>
			<td>Vetbond</td>
			<td>3M</td>
			<td>1469SB</td>
			<td>tissue adhesive</td>
		</tr>
		<tr>
			<td>WinDaq software</td>
			<td>DATAQ</td>
			<td></td>
			<td>recording software</td>
		</tr>
	</tbody>
</table>

long-term continuous measurement of renal blood flow in conscious rats

The kidneys play a crucial role in maintaining the homeostasis of body fluids. The regulation of renal blood flow (RBF) is essential to the vital functions of filtration and metabolism in kidney function. Many acute studies have been carried out in anesthetized animals to measure RBF under various conditions to determine mechanisms responsible for the regulation of kidney perfusion. However, for technical reasons, it has not been possible to measure RBF continuously (24 h/day) in unrestrained unanesthetized rats over prolonged periods. These methods allow the continuous determination of RBF over many weeks while also simultaneously recording blood pressure (BP) with implanted catheters (fluid-filled or by telemetry). RBF monitoring is carried out with rats placed in a circular servo-controlled rat cage that enables the unrestrained movement of the rat throughout the study. At the same time, the tangling of cables from the flow probe and arterial catheters is prevented. Rats are first instrumented with an ultrasonic flow probe placement on the left renal artery and an arterial catheter implanted in the right femoral artery. These are routed subcutaneously to the nape of the neck, and connected to the flowmeter and pressure transducer, respectively, to measure RBF and BP. Following surgical implantation, rats are immediately placed in the cage to recover for at least one week and stabilize the ultrasonic probe recordings. Urine collection is also feasible in this system. The surgical and post-surgical procedures for continuous monitoring are demonstrated in this protocol.

The mean arterial pressure data (Figure 1A) and blood flow data (Figure 1B) from a representative male Dahl salt-sensitive rat are shown. The Dahl salt-sensitive rats are maintained in a colony and bred at the Medical College of Wisconsin. The surgery was done at the age of 8 weeks, and the bodyweight was 249 g at the time of surgery. Rats were fed with a 0.4% NaCl diet, and the diet was changed to a 4% NaCl diet at the age of 10 weeks. Measurements were continu...

Watch this Scientific Journal Video about Long-Term Continuous Measurement of Renal Blood Flow in Conscious Rats at JoVE.com

Long-Term Continuous Measurement of Renal Blood Flow in Conscious Rats

The present protocol describes a long-term continuous measurement of renal blood flow in conscious rats and simultaneously recording blood pressure with implanted catheters (fluid-filled or by telemetry).

The kidneys play a crucial role in maintaining the homeostasis of body fluids. The regulation of renal blood flow (RBF) is essential to the vital ...

The continuous recording of renal blood flow in instrumented rats allows us to temporarily determine the sequence of events which lead up to the disease process that we're studying. In our case, it's hypertension and we're trying to determine whether a reduction of renal blood flow, which occurs in hypertension, precedes or is a consequence of the high blood pressure. The system that we'll be demonstrating today and the preparation of the animal is really designed to enable a continuous 24-hour determination of renal blood flow for many weeks at a time to study chronic events and to study the rat in their home environment, cages.As with all surgical techniques, practice, patience and attention to detail, we will required to master these procedures until the implement can be carried out on time. To begin shave the entire abdomen in a region on the nap around the seventh cervical vertebrae of an anesthetized rat with an electric clipper. After shaving, wipe the area three times alternating with 10%povidone iodine, and 70%ethanol.Place the rat in the prone position. Make a one centimeter cut with the scalpel on the nap and the left flank. Then perform a blunt dissection with hemostatic forceps in clear subcutaneous space from the flank incision to the back of the neck.Attach the skin button to the flow probe and pass the flow probe through this subcutaneous tunnel from the neck to the flank incision with hemostatic forceps. Then place the rat in the supine position and make a four to five centimeter midline abdominal incision. Dissect the area around the left renal artery with curved microdissecting forceps exposing the space sufficient to place the flow probe.Then bluntly, pierce the left quadratus lumbar muscle with the hemostatic forceps and pull the head of the flow probe through the renal artery under the fatty tissue into the abdominal cavity. Place the polyester fiber mesh on the abdominal wall. Hook the tip of the flow probe to the left renal artery and connect it to the flow meter.Add some gel around the probe tip and value of the flow rate will appear on the flow meter. Glue the polyester fiber mesh attached to the probe to the abdominal wall using tissue adhesive and hold until dry and bonded. Once the probe is in place, disconnect the flow probe from the flow meter and cover the abdomen with saline soaked gauze.To suture the probe, turn the rat to the prone position. Attach the skin button to the flow probe and make a circular loop of the flow probe subcutaneously at the flank. Suture the incision at the neck and the button to the skin.Then suture the flank with four ott surgical sutures. Connect the flow probe to the flow meter again, and turn the rat back to the dorsal position to check renal blood flow. Make final flow probe adjustments to optimize its position on the renal artery.Finally, suture the muscle with three ott silk in the skin with four ott surgical suture. When the rat is fully recovered from anesthesia return the rat to a movement response caging system connect the flow probe to the blood flow meter and allow a recovery period of about a week to stabilize the probe and flow measurement. The mean arterial pressure and blood flow were continuously measured in dull salt sensitive rats while switching from a low to high salt diet.This representative data from a male rat was recorded over a period of four weeks and is shown with a minute average. A clear diurnal difference was observed in mean arterial pressure and blood flow. While blood pressure increases with a high salt diet blood flow tends to decrease rather than increase suggesting increased renal vascular resistance.The great advantage of this technique is that it can study renal blood flow over long periods of time, and most importantly in unanesthetized conditions. This is of great importance when studying response to various stimuli where you can use the same animal under controlled unanesthetized conditions and follow that same animal over short periods or very long periods to see what the response is to some particular stimulus or pathological disease is.

long-term-continuous-measurement-of-renal-blood-flow-in-conscious-rats

Research

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Medicine

Automated Measurement of Microcirculatory Blood Flow Velocity in Pulmonary Metastases of Rats

Because the lung is a major target organ of metastatic disease, animal models to study the physiology of pulmonary metastases are of great importance. However, very few methods exist to date to investigate lung metastases in a dynamic fashion at the microcirculatory level, due to the difficulty to access the lung with a microscope. Here, an intravital microscopy method is presented to functionally image and quantify the microcirculation of superficial pulmonary metastases in rats, using a closed-chest pulmonary window and automated analysis of blood flow velocity and direction. The utility of this method is demonstrated to measure increases in blood flow velocity in response to pharmacological intervention, and to image the well-known tortuous vasculature of solid tumors. This is the first demonstration of intravital microscopy on pulmonary metastases in a closed-chest model. Because of its minimized invasiveness, as well as due to its relative ease and practicality, this technology has the potential to experience widespread use in laboratories that specialize on pulmonary tumor research.

A method is presented to measure microcirculatory blood flow velocity in pulmonary cancer metastases of the pleural surface in rats in an automated fashion, using closed-chest pulmonary intravital microscopy. This model has potential to be used as a widespread tool to perform physiologic research on pulmonary metastases in rodents.

Because the lung is a major target organ of metastatic disease, animal models to study the physiology of pulmonary metastases are of great importance. ...

Early Detection of Drug-Induced Renal Hemodynamic Dysfunction Using Sonographic Technology in Rats

The kidney normally functions to maintain hemodynamic homeostasis and is a major site of damage caused by drug toxicity. Drug-induced nephrotoxicity is estimated to contribute to 19- 25% of all clinical cases of acute kidney injury (AKI) in critically ill patients. AKI detection has historically relied on metrics such as serum creatinine (sCr) or blood urea nitrogen (BUN) which are demonstrably inadequate in full assessment of nephrotoxicity in the early phase of renal dysfunction. Currently, there is no robust diagnostic method to accurately detect hemodynamic alteration in the early phase of AKI while such alterations might actually precede the rise in serum biomarker levels. Such early detection can help clinicians make an accurate diagnosis and help in in decision making for therapeutic strategy. Rats were treated with Cisplatin to induce AKI. Nephrotoxicity was assessed for six days using high-frequency sonography, sCr measurement and upon histopathology of kidney. Hemodynamic evaluation using 2D and Color-Doppler images were used to serially study nephrotoxicity in rats, using the sonography. Our data showed successful drug-induced kidney injury in adult rats by histological examination. Color-Doppler based sonographic assessment of AKI indicated that resistive-index (RI) and pulsatile-index (PI) were increased in the treatment group; and peak-systolic velocity (mm/s), end-diastolic velocity (mm/s) and velocity-time integral (VTI, mm) were decreased in renal arteries in the same group. Importantly, these hemodynamic changes evaluated by sonography preceded the rise of sCr levels. Sonography-based indices such as RI or PI can thus be useful predictive markers of declining renal function in rodents. From our sonography-based observations in the kidneys of rats that underwent AKI, we showed that these noninvasive hemodynamic measurements may consider as an accurate, sensitive and robust method in detecting early stage kidney dysfunction. This study also underscores the importance of ethical issues associated with animal use in research.

Early stage hemodynamic dysfunction is critical to the development of kidney disease. Yet, detection methodologies are limited. Recent advances in sonography provide a noninvasive, accurate option for early detection of kidney injury. This study outlines a step-by-step, sonographic methodology for detecting kidney dysfunction using a drug-induced nephrotoxicity rat model.

The kidney normally functions to maintain hemodynamic homeostasis and is a major site of damage caused by drug toxicity. Drug-induced nephrotoxicity is ...

Transcutaneous Assessment of Renal Function in Conscious Rodents

Glomerular filtration rate (GFR) is the gold standard to assess overall kidney function. However, traditional methods to evaluate GFR are cumbersome and time-consuming. In addition, serial blood or urine samples are required, with the associated stress for the experimental animals. A recent technique significantly reduces the investment in time and resources, minimizing the invasiveness and the animal stress, but being equally valid as the traditional approaches. The method measures transcutaneously renal function. Using an optical device and the exogenous renal marker fluorescein isothiocyanate (FITC)-sinistrin, this technique is capable of measuring the elimination kinetics of the marker through the skin. With neither blood nor urine samples nor the associated laboratory assays needed, the results of the transcutaneous measurement are almost instantaneously available. The method has been already validated in different species and successfully applied in several models of renal pathology. Moreover, due to its minimally invasive characteristics, it is suitable for sequential measurements within the same animal. Here is provided a detailed protocol to carry out the transcutaneous assessment of renal function in rodents.

Determination of glomerular filtration rate (GFR) is the gold standard to assess overall kidney function. However, traditional procedures to measure this parameter are cumbersome and require a large investment of time. Here we describe a faster and minimally invasive method to determinate GFR transcutaneously.

Glomerular filtration rate (GFR) is the gold standard to assess overall kidney function. However, traditional methods to evaluate GFR are cumbersome and ...

Surgical Placement of Catheters for Long-term Cardiovascular Exercise Testing in Swine

This protocol describes the surgical procedure to chronically instrument swine and the procedure to exercise swine on a motor-driven treadmill. Early cardiopulmonary dysfunction is difficult to diagnose, particularly in animal models, as cardiopulmonary function is often measured invasively, requiring anesthesia. As many anesthetic agents are cardiodepressive, subtle changes in cardiovascular function may be masked. In contrast, chronic instrumentation allows for measurement of cardiopulmonary function in the awake state, so that measurements can be obtained under quiet resting conditions, without the effects of anesthesia and acute surgical trauma. Furthermore, when animals are properly trained, measurements can also be obtained during graded treadmill exercise.
Flow probes are placed around the aorta or pulmonary artery for measurement of cardiac output and around the left anterior descending coronary artery for measurement of coronary blood flow. Fluid-filled catheters are implanted in the aorta, pulmonary artery, left atrium, left ventricle and right ventricle for pressure measurement and blood sampling. In addition, a 20 G&#160;catheter is positioned in the anterior interventricular vein to allow coronary venous blood sampling.
After a week of recovery, swine are placed on a motor-driven treadmill, the catheters are connected to pressure and flow meters, and swine are subjected to a five-stage progressive exercise protocol, with each stage lasting 3 min. Hemodynamic signals are continuously recorded and blood samples are taken during the last 30 sec of each exercise stage.
The major advantage of studying chronically instrumented animals is that it allows serial assessment of cardiopulmonary function, not only at rest but also during physical stress such as exercise. Moreover, cardiopulmonary function can be assessed repeatedly during disease development and during chronic treatment, thereby increasing statistical power and hence limiting the number of animals required for a study.

Here we present a protocol to assess cardiopulmonary function in awake swine, at rest and during graded treadmill exercise. Chronic instrumentation allows for repeated hemodynamic measurements uninfluenced by cardiodepressive anesthetic agents.

This protocol describes the surgical procedure to chronically instrument swine and the procedure to exercise swine on a motor-driven treadmill. Early ...

Long-term Blood Pressure Measurement in Freely Moving Mice Using Telemetry

During the development of new vasoactive agents, arterial blood pressure monitoring is crucial for evaluating the efficacy of the new proposed drugs. Indeed, research focusing on the discovery of new potential therapeutic targets using genetically altered mice requires a reliable, long-term assessment of the systemic arterial pressure variation. Currently, the gold standard for obtaining long-term measurements of blood pressure in ambulatory mice uses implantable radio-transmitters, which require&#160;artery cannulation. This technique eliminates the need for tethering, restraining, or anesthetizing the animals which introduce stress and artifacts during data sampling. However, arterial blood pressure monitoring in mice via catheterization can be rather challenging due to the small size of the arteries. Here we present a step-by-step guide to illustrate the crucial key passages for a successful subcutaneous implantation of radio-transmitters and carotid artery cannulation in mice. We also include examples of long-term blood pressure activity taken from freely moving mice after a period of post-surgery recovery. Following this procedure will allow reliable direct blood pressure recordings from multiple animals simultaneously.

The goal of this protocol is to assess systemic blood pressure in conscious freely moving mice using implantable radio-telemetry devices.

During the development of new vasoactive agents, arterial blood pressure monitoring is crucial for evaluating the efficacy of the new proposed drugs. ...

Novel Approach for Simultaneous Recording of Renal Sympathetic Nerve Activity and Blood Pressure with Intravenous Infusion in Conscious, Unrestrained Mice.

Renal sympathetic nerves contribute significantly to both physiological and pathophysiological phenomena. Evaluating renal sympathetic nerve activity (RSNA) is of great interest in many areas of research such as chronic kidney disease, hypertension, heart failure, diabetes and obesity. Unequivocal assessment of the role of the sympathetic nervous system is thus imperative for proper interpretation of experimental results and understanding of disease processes. RSNA has been traditionally measured in anesthetized rodents, including mice. However, mice usually exhibit very low systemic blood pressure and hemodynamic instability for several hours during anesthesia and surgery. Meaningful interpretation of RSNA is confounded by this non-physiological state, given the intimate relationship between sympathetic nervous tone and cardiovascular status. To address this limitation of traditional approaches, we developed a new method for measuring RSNA in conscious, freely-moving mice. Mice were chronically instrumented with radio-telemeters for continuous monitoring of blood pressure as well as a jugular venous infusion catheter and custom-designed bipolar electrode for direct recording of RSNA. Following a 48-72 hour recovery period, survival rate was 100% and all mice behaved normally. At this time-point, RSNA was successfully recorded in 80% of mice, with viable signals acquired up to 4 and 5 days post-surgery in 70% and 50% of mice, respectively. Physiological blood pressures were recorded in all mice (116&plusmn;2 mmHg; n=10). Recorded RSNA increased with eating and grooming, as well-established in the literature. Furthermore, RSNA was validated by ganglionic blockade and modulation of blood pressure with pharmacological agents. Herein, an effective and manageable method for clear recording of RSNA in conscious, freely-moving mice is described.

Anesthetized mice exhibit non-physiological systemic blood pressure, which precludes meaningful assessment of autonomic tone given the intimate relationship between blood pressure and the autonomic nervous system. Thus, a novel method to simultaneously record renal sympathetic nerve activity and blood pressure with intravenous infusion in conscious mice is outlined.

Renal sympathetic nerves contribute significantly to both physiological and pathophysiological phenomena. Evaluating renal sympathetic nerve activity ...

Simultaneous Electrocardiography Recording and Invasive Blood Pressure Measurement in Rats

For studies related to cardiovascular physiology or pathophysiology, blood pressure (BP) and electrocardiography are basic observational parameters. Research focusing on cardiovascular disease models, potential cardiovascular therapeutic targets or pharmaceutical agents requires assessment of systemic arterial pressure and heart rhythm changes. In situations where radio telemetry systems are not available or affordable, the technique of femoral artery cannulation is an alternative way to obtain intra-arterial pressure waveform recordings and systemic BP measurements. This technique is economical and can be performed with standard equipment in animal facilities. However, invasive arterial pressure recording requires cannulation of small arteries, which can be a challenging surgical skill. Here, we present step-by-step protocols for femoral artery cannulation procedures. Key procedures include the calibration of the data acquisition system, tissue dissection and femoral artery cannulation, and setup of the arterial cannulation system for pressure recording. Surface electrocardiography recording procedures are also included. We also present examples of BP recordings from normotensive and hypertensive rats. This protocol allows reliable direct recordings of systemic BP with simultaneous electrocardiography.

Here, we describe a setup for simultaneous recording of electrocardiography and intra-arterial blood pressure (BP) in experimental rats, which can be done with standard equipment in animal facilities and can be applied to physiological or pharmacological studies to investigate pathogenic or therapeutic mechanisms in cardiovascular medicine.

For studies related to cardiovascular physiology or pathophysiology, blood pressure (BP) and electrocardiography are basic observational parameters. ...

Continuous Blood Sampling in Small Animal Positron Emission Tomography/Computed Tomography Enables the Measurement of the Arterial Input Function

For quantitative analysis and bio-kinetic modeling of positron emission tomography/computed tomography (PET/CT) data, the determination of the temporal blood time-activity concentration also known as arterial input function (AIF) is a key point, especially for the characterization of animal disease models and the introduction of newly developed radiotracers. The knowledge of radiotracer availability in the blood helps to interpret PET/CT-derived data of tissue activity. For this purpose, online blood sampling during the PET/CT imaging is advisable to measure the AIF. In contrast to manual blood sampling and image-derived approaches, continuous online blood sampling has several advantages. Besides the minimized blood loss, there is an improved resolution and a superior accuracy for the blood activity measurement. However, the major drawback of online blood sampling is the costly and time-consuming preparation to catheterize the femoral vessels of the animal. Here, we describe an easy and complete workflow for catheterization and continuous blood sampling during small animal PET/CT imaging and compared it to manual blood sampling and an image-derived approach. Using this highly-standardized workflow, the determination of the fluorodeoxyglucose ([18F]FDG) AIF is demonstrated. Further, this procedure can be applied to any radiotracer in combination with different animal models to create fundamental knowledge of tracer kinetic and model characteristics. This allows a more precise evaluation of the behavior of pharmaceuticals, both for diagnostic and therapeutic approaches in the preclinical research of oncological, neurodegenerative and myocardial diseases.

Here a protocol for continuous blood sampling during PET/CT imaging of rats to measure the arterial input function (AIF) is described. The catheterization, the calibration and setup of the system and the data analysis of the blood radioactivity are demonstrated. The generated data provide input parameters for subsequent bio-kinetic modeling.

For quantitative analysis and bio-kinetic modeling of positron emission tomography/computed tomography (PET/CT) data, the determination of the temporal ...

Hemocompatibility Testing of Blood-Contacting Implants in a Flow Loop Model Mimicking Human Blood Flow

The growing use of medical devices (e.g., vascular grafts, stents, and cardiac catheters) for temporary or permanent purposes that remain in the body&#39;s circulatory system demands a reliable and multiparametric approach that evaluates the possible hematologic complications caused by these devices (i.e., activation and destruction of blood components). Comprehensive in vitro hemocompatibility testing of blood-contacting implants is the first step towards successful in vivo implementation. Therefore, extensive analysis according to the International Organization for Standardization 10993-4 (ISO 10993-4) is mandatory prior to clinical application. The presented flow loop describes a sensitive model to analyze the hemostatic performance of stents (in this case, neurovascular) and reveal adverse effects. The use of fresh human whole blood and gentle blood sampling are essential to avoid the preactivation of blood. The blood is perfused through a heparinized tubing containing the test specimen by using a peristaltic pump at a rate of 150 mL/min at 37 &#176;C for 60 min. Before and after perfusion, hematologic markers (i.e., blood cell count, hemoglobin, hematocrit, and plasmatic markers) indicating the activation of leukocytes (polymorphonuclear [PMN]-elastase), platelets (&#946;-thromboglobulin [&#946;-TG]), the coagulation system (thombin-antithrombin III [TAT]), and the complement cascade (SC5b-9) are analyzed. In conclusion, we present an essential and reliable model for extensive hemocompatibility testing of stents and other blood-contacting devices prior to clinical application.

This protocol describes a comprehensive hemocompatibility evaluation of blood-contacting devices using laser-cut neurovascular implants. A flow loop model with fresh, heparinized human blood is applied to mimic blood flow. After perfusion, various hematologic markers are analyzed and compared to the values gained directly after blood collection for hemocompatibility evaluation of the tested devices.

The growing use of medical devices (e.g., vascular grafts, stents, and cardiac catheters) for temporary or permanent purposes that remain in the ...

Measurement of Strial Blood Flow in Mouse Cochlea Utilizing an Open Vessel-Window and Intravital Fluorescence Microscopy

Transduction of sound is metabolically demanding, and the normal function of the microvasculature in the lateral wall is critical for maintaining endocochlear potential, ion transport, and fluid balance. Different forms of hearing disorders are reported to involve abnormal microcirculation in the cochlea. Investigation of how cochlear blood flow (CoBF) pathology affects hearing function is challenging due to the lack of feasible interrogation methods and the difficulty in accessing the inner ear. An open vessel-window in the lateral cochlear wall, combined with fluorescence intravital microscopy, has been used for studying CoBF changes in vivo, but mostly in guinea pig and only recently in the mouse. This paper and the associated video describe the open vessel-window method for visualizing blood flow in the mouse cochlea. Details include 1) preparation of the fluorescent-labeled blood cell suspension from mice; 2) construction of an open vessel-window for intravital microscopy in an anesthetized mouse, and 3) measurement of blood flow velocity and volume using an offline recording of the imaging. The method is presented in video format to show how to use the open window approach in mouse to investigate structural and functional changes in the cochlear microcirculation under normal and pathological conditions.

An open vessel-window approach using fluorescent tracers provides sufficient resolution for cochlear blood flow (CoBF) measurement. The method facilitates the study of structural and functional changes in CoBF in mouse under normal and pathological conditions.