Name: ultrasound assessment of flow-mediated dilation of the brachial and superficial femoral arteries in rats
Uploaded: 2016-11-03T13:00:00
Description: Watch this Scientific Journal Video about Ultrasound Assessment of Flow-Mediated Dilation of the Brachial and Superficial Femoral Arteries in Rats at JoVE.com

All animal imaging was performed at the Small Animal Imaging Core Facility, University of Utah.
This study was funded in part by grants from the National Institutes of Health (R21 AG043952, R01 AG040297, K01 AG046326, K02 AG045339, and R01 DK100505).

All animal procedures conformed to the Guide for the Care and Use of Laboratory Animals14 and were approved by the University of Utah and Salt Lake City Veterans Affairs Medical Center Animal Care and Use.
1. Animal Preparation
<ol>
	<li>Place animal in anesthesia induction chamber containing 3% isoflurane in 100% oxygen. Leave the animal in the induction chamber until it is unresponsive to external stimuli.</li>
	<li>Remove the animal from the induction chamber and place it on a ...

<ol>
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In the present study, a non-invasive measurement of FMD was demonstrated in the brachial and superficial femoral arteries of rats. Similar to humans6, following a 5 min occlusion period, there was a rapid increase in blood velocity (i.e., reactive hyperemia) thereby increasing shear rate on the arterial wall which resulted in the subsequent vasodilation of the artery. FMD was observed in both the brachial and superficial femoral arteries. Additionally, there was a strong relationship in FMD between arteries. A...

The vascular endothelium is a cellular monolayer that lines the lumen of arteries and is an important regulator of vascular function. There are numerous molecules released from the endothelium that result in modulation of blood vessel diameter. Among these molecules, nitric oxide (NO), appears to be the primary vasodilatory molecule released from the vascular endothelium in response to stimulation (e.g., insulin, acetylcholine, or changes in shear stress)1. In the vascular endothelium, NO is produced by the enzyme endothelial NO synthase (eNOS) and is subsequently released from endothelial cells2. NO diffuses to the vascular smooth muscle where it causes relaxation and increased vessel diameter3.
Endothelial dysfunction can be assessed non-invasively in humans using the flow-mediated dilation (FMD) technique4,5. FMD has been proposed to represent a functional bioassay for endothelium-derived NO bioavailability in humans, and is typically assessed at the brachial or superficial femoral artery in response to reactive hyperemia following a ~5 min limb occlusion6. Reactive hyperemia increases laminar shear forces that are transduced to the endothelial cell7, signaling a release of NO8. Although in recent years, the proportion of vasodilation initiated by NO release has been debated9,10, FMD is indicative of endothelium-dependent dilation and has consistently been shown to predict cardiovascular events11-13.
To date, thousands of studies have employed the FMD technique for non-invasive measurement of endothelial function in humans. Considering the recent shift in focus to translational research, guidelines for the non-invasive measurement of FMD in rodents would be extremely valuable. Keeping with a translational approach, this protocol was established for measurement of FMD in brachial and superficial femoral arteries of rats, as those sites are most commonly measured in humans. This protocol results in a robust and repeatable FMD response in rats, however, measurement of FMD in rats is technically demanding and may be difficult for other investigators to replicate without video demonstration. Therefore, the following article will demonstrate a method for the non-invasive measurement of FMD in the brachial and superficial femoral arteries of rats.

<table border="0" cellpadding="0" cellspacing="0" width="710">
	<tbody>
		<tr height="58">
			<td height="58" style="height:58px;width:203px;">Vevo 2100 High Resolution Micro-Ultrasound Imaging System</td>
			<td style="width:169px;">VisualSonics, Toronto, ON, CAN</td>
			<td style="width:169px;"></td>
			<td style="width:169px;"></td>
		</tr>
		<tr height="77">
			<td height="77" style="height:77px;width:203px;">MicroScan Ultra-High Frequency Linear Array Transducer - MS-700 30-70 MHz</td>
			<td style="width:169px;">VisualSonics, Toronto, ON, CAN</td>
			<td style="width:169px;"></td>
			<td style="width:169px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:203px;">Vevo Imaging Station</td>
			<td style="width:169px;">VisualSonics, Toronto, ON, CAN</td>
			<td style="width:169px;"></td>
			<td style="width:169px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:203px;">Thermasonic gel warmer</td>
			<td style="width:169px;">Parker Laboratories, Fairfield, NJ, USA</td>
			<td style="width:169px;">82-03</td>
			<td style="width:169px;">Optional</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:203px;">Signacreme electrode cream</td>
			<td style="width:169px;">Parker Laboratories, Fairfield, NJ, USA</td>
			<td style="width:169px;">17-05</td>
			<td style="width:169px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:203px;">Transpore surgical tape</td>
			<td style="width:169px;">3M, Maplewood, MN, USA</td>
			<td style="width:169px;">1527-1</td>
			<td style="width:169px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:203px;">Depilatory cream (e.g., Nair)</td>
			<td style="width:169px;">General supply</td>
			<td style="width:169px;"></td>
			<td style="width:169px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:203px;">Cotton swabs</td>
			<td style="width:169px;">General supply</td>
			<td style="width:169px;"></td>
			<td style="width:169px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:203px;">Ultrasound gel</td>
			<td style="width:169px;">General supply</td>
			<td style="width:169px;"></td>
			<td style="width:169px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:203px;">Standard vascular occluder, 10 mm lumen diameter</td>
			<td style="width:169px;">Harvard Apparatus, Holliston, MA, USA</td>
			<td style="width:169px;">62-0115</td>
			<td style="width:169px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:203px;">10 ml syringe with Luer-Lok tip</td>
			<td style="width:169px;">General Supply</td>
			<td style="width:169px;"></td>
			<td style="width:169px;">Used for occlusion cuff apparatus</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:203px;">Paperclip</td>
			<td style="width:169px;">General Supply</td>
			<td style="width:169px;"></td>
			<td style="width:169px;">Used for occlusion cuff apparatus</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:203px;">Hypodermic needle &#8211; 18 gauge&#160;</td>
			<td style="width:169px;">General Supply</td>
			<td style="width:169px;"></td>
			<td style="width:169px;">Used for occlusion cuff apparatus</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:203px;">Medium binder clip</td>
			<td style="width:169px;">General Supply</td>
			<td style="width:169px;"></td>
			<td style="width:169px;">Used for occlusion cuff apparatus</td>
		</tr>
	</tbody>
</table>

ultrasound assessment of flow-mediated dilation of the brachial and superficial femoral arteries in rats

Arterial vasodilation to increases in wall shear rate is indicative of vascular endothelial function. In humans, the non-invasive measurement of endothelial function can be achieved by employing the flow-mediated dilation technique, typically performed in the brachial or superficial femoral artery. Briefly, a blood pressure cuff placed distal to an ultrasound probe is inflated to a suprasystolic pressure, which results in limb ischemia. After 5 min of occlusion the cuff is deflated, resulting in reactive hyperemia and increases in wall shear rate that signal vasodilatory molecules to be released from the endothelium eliciting vasodilation. Despite the thousands of studies performing flow-mediated dilation in humans, surprisingly, no studies have performed this technique non-invasively in living rats. Considering the recent shift in focus to translational research, the establishment of guidelines for non-invasive measurement of flow-mediated dilation in rats and other rodents would be extremely valuable. In the following article, a protocol is presented for the non-invasive measurement of flow-mediated dilation in brachial and superficial femoral arteries of rats, as those sites are most commonly measured in humans.

Flow-mediated dilation was performed on the brachial and superficial femoral artery of 8 Wistar rats. Positioning of a rat is shown in Figure 1.
Representative ultrasound images of the superficial femoral artery are shown in Figure 2.
<img alt="Figure 1" src="/files/ftp_upload/54762/54762fig1.jpg" /> 
Figure 1. <s...

Watch this Scientific Journal Video about Ultrasound Assessment of Flow-Mediated Dilation of the Brachial and Superficial Femoral Arteries in Rats at JoVE.com

Ultrasound Assessment of Flow-Mediated Dilation of the Brachial and Superficial Femoral Arteries in Rats

Non-invasive assessment of endothelial function in humans can be determined by the flow-mediated dilation technique. Although thousands of studies have used this technique, no study has performed this technique non-invasively in rats. The following article describes non-invasive measurement of flow-mediated dilation in the brachial and superficial femoral arteries of rats.

Arterial vasodilation to increases in wall shear rate is indicative of vascular endothelial function. In humans, the non-invasive measurement of ...

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