In Vivo Luminal Measurement of Distension-Evoked Urothelial ATP Release in Rodents

Summary

This protocol describes the procedure for measuring ATP concentrations in the lumen of the bladder in an anesthetized rodent.

Abstract

ATP, released from the urothelium in response to bladder distension, is thought to play a significant sensory role in the control of micturition. Therefore, accurate measurement of urothelial ATP release in a physiological setting is an important first step in studying the mechanisms that control purinergic signaling in the urinary bladder. Existing techniques to study mechanically evoked urothelial ATP release utilize cultured cells plated on flexible supports or bladder tissue pinned into Ussing chambers; however, each of these techniques does not fully emulate conditions in the intact bladder. Therefore, an experimental setup was developed to directly measure ATP concentrations in the lumen of the rodent urinary bladder.

In this setup, the bladders of anesthetized rodents are perfused through catheters in both the dome of the bladder and via the external urethral orifice. Pressure in the bladder is increased by capping the urethral catheter while perfusing sterile fluid into the bladder through the dome. Measurement of intravesical pressure is achieved using a pressure transducer attached to the bladder dome catheter, akin to the setup used for cystometry. Once the desired pressure is reached, the urethral catheter's cap is removed, and fluid collected for ATP quantification by luciferin-luciferase assay. Through this experimental setup, the mechanisms controlling both mechanical and chemical stimulation of urothelial ATP release can be interrogated by including various agonists or antagonists into the perfusate or by comparing results between wildtype and genetically modified animals.

Introduction

Urinary ATP is thought to play a significant sensory role in the control of micturition¹. For example, it is thought that ATP is released from the urothelium in response to distension where it can act on receptors on bladder afferent nerves to increase their excitability, leading to sensations of fullness². Thus, it is also thought that urinary ATP could be an important player in the development of bladder pathologies. In support of this hypothesis, urinary ATP concentrations are significantly increased in patients suffering from overactive bladder (OAB)³, bladder pain syndrome/interstitial cystit....

Protocol

All procedures carried out in rodents must adhere to the applicable guidelines and be approved by the local institutional ethics review committee. The experiments performed for this manuscript were carried out in accordance with the National Research Council's Guide for the Care and Use of Laboratory Animals and approved by the Institutional Animal Care and Use Committee (IACUC) of the University of Pittsburgh School of Medicine. See Figure 1 for a modified version of the standard rodent.......

Discussion

The majority of research into urothelial ATP release is conducted in cultured cells, using either immortalized cell lines or primary cultures of rodent urothelial cells. While these models have the benefit of being relatively high throughput (i.e., one culture/passage can make many plates/dishes of cells), their physiological relevance is diminished due to: 1) the inability of urothelial cells to grow polarized unless they are grown on special supports and 2) the difficulty in exposing cultured cells to physiological lev.......

Materials

Name	Company	Catalog Number	Comments
amplifier	World Precision Instruments (WPI)	SYS-TBM4M
ATP assay kit	Sigma-Aldrich, Inc.	FLAA-1KT
data acquisition system/ software	DataQ Instruments	DI-1100	Software included, requires Windows-based computer
Hexamethonium bromide	Sigma-Aldrich, Inc.	H0879	20 mg/kg dose
Isoflurane	Covetrus North America	29404
lidocaine	Covetrus North America	2468
Luer Lock plugs	Fisher Scientific	NC0455253
luminometer (GloMax 20/20)	Promega	E5311
Polyethylene (PE50) tubing	Fisher Scientific	14-170-12B
Pump 33 DDS syringe pump	Harvard Apparatus	703333
pressure transducers	World Precision Instruments (WPI)	BLPR2
surgical instruments (scissors, hemostats, forceps, etc.)	Fine Science Tools	multiple numbers
surgical lubricant	Fisher Scientific	10-000-694
Sur-Vet I.V. catheter	Covetrus North America	50603	20 G x 1 inch
tiltable surgical table (Plas Labs)	Fisher Scientific	01-288-30A
Tubing connectors	Fisher Scientific	14-826-19E	allows Luer-Lock connectors to attach to tubing
Urethane	Sigma-Aldrich, Inc.	U2500	0.5 g/mL conc., 1.2 g/kg dose