Effects of Nitric Oxide on Bladder Outlet Obstruction in Rats

We investigated the changes in bladder function resulting from bladder outlet obstruction (BOO), with particular emphasis on the role of nitric oide (NO) in bladder response. Twelve-week-old female Wistar rats (n = 36) were surgically treated in various ways by dividing them into 6 groups each with 6 animals: 2 sham-operated groups, 2 obstructed groups for 1 week or 6 weeks, and 2 groups obstructed and intraperitoneally injected with 150-mg/kg L-arginine once daily for 1 week or 6 weeks. We conducted bladder strip stimulation studies using carbachol and KCl. Then the bladder was used for measurement of NO synthase (NOS) activity and was also studied histologically using immunohistochemical staining. Bladders in the obstructed groups were significantly heavier than in the sham-operated groups. The mean weight of bladders in the groups obstructed and treated with L-arginine was almost the same as that in the sham-operated groups. Tissue bath studies demonstrated decreased contractility in response to cholinergic stimulation at obstruction, but contractility at obstruction was improved by L-arginine for 1 week or 6 weeks. NOS activity in bladder tissue was lower in the obstructed groups than in the sham groups, and higher in the L-arginine-combined groups than in the obstructed groups. These results indicate that bladder dysfunction may be improved by treatment with L-arginine. This study suggests that increased NO by treatment with L-arginine plays a role in improving bladder dysfunction caused by BOO.