Effects of L-Arginine on Bladder Function in Bladder Outlet-Obstructed Rats

Nitric oxide (NO) is thought to play an important role in the lower urinary tract. We therefore studied the effects of NO on bladder function in bladder outlet-obstructed rats. Twelve-week-old female Wistar rats had their bladder outlets partially obstructed by ligating the urethra over which a catheter was placed. Micturition parameters and urodynamic parameters were measured in 6 groups of rats: Group I, 1 week after sham operation; Group II, 1 week after surgical induction of bladder outlet obstruction; Group III, 150-mg/kg/day L-arginine injected intraperitoneally for 1 week after surgical induction of bladder outlet obstruction; Group IV, 6 weeks after sham operation; Group V, 6 weeks after surgical induction of bladder outlet obstruction and Group VI, 150-mg/kg/day L-arginine injected intraperitoneally for 6 weeks after surgical induction of bladder outlet obstruction. Moreover, the area density of smooth muscle versus connective tissue was determined in bladder specimens using color assisted computer image analysis in these groups. The number of micturitions per day of the 1- and 6-week obstructed rats significantly increased over that of the sham-operated rats. The number of micturitions per day of the obstructed rats treated with L-arginine for 1 and 6 weeks significantly decreased in comparison to that of the obstructed rats. In the urodynamic study, the maximum detrusor pressure of the obstructed rats for 1 and 6 weeks significantly increased over that of the sham-operated rats. Residual urine volume of the obstructed rats for 1 and 6 weeks significantly increased over that of the sham-operated rats. The maximum detrusor pressure and residual urine volume of the obstructed rats treated with L-arginine for 1 and 6 weeks significantly decreased over those of the obstructed rats. In the histological study, the area density of smooth muscle versus connective tissue of the 1- and 6-week obstructed rats significantly increased over that of the sham-operated rats. Histological changes in the 1- and 6-week obstructed rats were prevented by treatment with L-arginine. These results indicate that L-arginine has a beneficial effect on bladder dysfunction in bladder outlet-obstructed rats. This might be due to L-arginine's influence in increasing NO levels and the rate of blood flow in the obstructed bladder.