Effect of glycine on recovery of bladder smooth muscle contractility after acute urinary retention in rats

Abstract

OBJECTIVE: To investigate the effects of glycine on the recovery of bladder smooth muscle contractility after acute urinary retention. MATERIALS AND METHODS: Bladder overdistension was induced in Sprague-Dawley rats by an infusion of saline (twice the threshold volume), maintained for 2 h. From 15 min before emptying of the bladder until 2 h after, saline or glycine solution was infused i.v. At 30 min, 2 h and 1 week after bladder emptying, samples of bladder tissue were taken for muscle strip study, malondialdehyde (MDA) assay, ATP assay, Western blotting for apoptosis-related molecules (Bcl-2, Bax, Caspase-3), and histological analysis including terminal deoxynucleotidyl transferase-mediated nick-end labelling staining. The results were compared among normal control, saline-treated and glycine-treated rats. RESULTS: In the glycine-treated group, muscle strip contractile responses induced by electrical-field stimulation and carbachol were both significantly greater at 1 week after bladder emptying than in the saline-treated group. The results of the ATP assay appeared to correspond with those of the muscle strip study. The saline-treated group had significantly higher MDA levels at 30 min after bladder emptying than the glycine-treated group. At 2 h after bladder emptying, there was significantly more apoptosis and greater leukocyte infiltration in the saline-treated group than in the glycine-treated group. While pro-apoptotic Bax and caspase-3 were down-regulated, Bcl-2 was up-regulated in the glycine-treated group. CONCLUSION: Glycine infusions might improve the contractile responses of bladder smooth muscle after acute urinary retention by reducing oxidative damage and apoptosis.