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

Objectives. Evidence is accumulating that bladder dysfunction caused by exp erimental partial obstruction of the bladder outlet can be reduced or rever sed by treatment that results in upregulation of bladder function, even in the presence of obstruction. Inducing diuresis in rats or rabbits results i n a significant increase in bladder mass and increased contractility in res ponse to stimulation. The objective of the present study was to determine w hether 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. Gr oups 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 exc ised and cut into longitudinal strips; each strip was mounted in an isolate d muscle bath for contractile studies. Results. Sucrose-induced diuresis caused a moderate but significant increas e in bladder mass. Partial outlet obstruction stimulated significant increa ses in bladder mass in both water-drinking and sucrose-drinking groups; the bladder mass of sucrose-drinking rats, however, increased less than that o f water-drinking rats. In water-drinking rats, partial outlet obstruction r esulted in significantly decreased bladder strip contractility in vitro in response to field stimulation (1 to 32 Hz), carbachol (0.1 to 22 mu M), and KCl (120 mM). After 3 weeks of sucrose-induced diuresis, partial obstructi on of the rat bladder outlet did not result in decreased in vitro contracti le responses to any form of stimulation applied. Conclusions. Sucrose-induced diuresis caused an increase in bladder mass an d an increase in contractile strength, consequently protecting the rat blad der from the contractile dysfunctions that usually follow partial outlet ob struction. UROLOGY 54: 183-187, 1999, (C) 1999, Elsevier Science Inc.