Sucrose diuresis protects rat bladder from outlet partial obstruction-induced contractile dysfunction

Abstract

Objectives. Evidence is accumulating that bladder dysfunction caused by experimental partial obstruction of the bladder outlet can be reduced or reversed by treatment that results in upregulation of bladder function, even in the presence of obstruction. Inducing diuresis in rats or rabbits results in a significant increase in bladder mass and increased contractility in response to stimulation. The objective of the present study was to determine whether diuresis-induced amplification of bladder function in the rat could protect the bladder from contractile dysfunctions caused by partial outlet obstruction. Methods. Thirty-two rats were separated into four groups of 8 rats each. Groups 2 and 4 were fed 5% sucrose instead of water; groups 1 and 3 were fed only water. Three weeks later, partial outlet obstructions were created in groups 3 and 4. After 4 weeks of obstruction, all bladders were rapidly excised and cut into longitudinal strips; each strip was mounted in an isolated muscle bath for contractile studies. Results. Sucrose-induced diuresis caused a moderate but significant increase in bladder mass. Partial outlet obstruction stimulated significant increases in bladder mass in both water-drinking and sucrose-drinking groups; the bladder mass of sucrose-drinking rats, however, increased less than that of water-drinking rats. In water-drinking rats, partial outlet obstruction resulted in significantly decreased bladder strip contractility in vitro in response to field stimulation (1 to 32 Hz), carbachol (0.1 to 22 μM), and KCl (120 mM). After 3 weeks of sucrose-induced diuresis, partial obstruction of the rat bladder outlet did not result in decreased in vitro contractile responses to any form of stimulation applied. Conclusions. Sucrose-induced diuresis caused an increase in bladder mass and an increase in contractile strength, consequently protecting the rat bladder from the contractile dysfunctions that usually follow partial outlet obstruction.