Effect of Nitric Oxide Generated by Photolysis on the Rat Detrusor

Chung, Byung Ha; Chang, Ki Churl; Choi, Seung Kang

Abstract

The mechanism underlying the bladder relaxation during filling is not fully understood. Nitric oxide played an important role in mediation of relaxation in between vascular and various types of non-vascular smooth muscle. Theoretically, an increased activity of nitric oxide-releasing inhibitory nerves to the detrusor could be a factor keeping the bladder relaxed during the filling phase. The role of nitric oxide in detrusor muscle is still not fully characterized. The objective of this study was to determine the effect and action mechanism of nitric oxide in the rat detrusor. In this experiment, nitric oxide was generated by photolysis using a long wavelength UV lamp ( 366nm) under nitric oxide, NO2-carrying molecules( streptozotocin, NG-nitro-L-arginine). This study were consisted of in vitro examination using Polygraph(Grass Model 79E, Quincy, MA, U.S.A.), radioimmunoassay for guanosine 3', 5'-cyclic monophosphate and nitrite assay to identify the production of nitric oxide. Nitric oxide was generated by photolysis from nitric oxide and NO-containing compounds. The longer UV irradiated and the stronger photo energy of light source, the more produced the amount of nitric oxide. The relaxation induced by nitric oxide-containing compound ( streptozotocin) is much more than that by NO2-containing compound(NG-nitro-L-arginine). Nitric oxide was a potent but labile relaxing substance to the rat detrusor strip. The maximal relaxation under streptozotocin treatment and 60 second UV irradiation was approximately 70.0 % comparing to carbachol induced contraction. That relaxation was significantly inhibited by pyrogallol, methylene blue treatment. The photo-induced nitric oxide directly activated soluble form of guanylate cyclase resulting in increased concentration of guanosine 3' 5'-cyclic monophosphate in detrusor strips. From the above results. it was confirmed that nitric oxide relaxed the detrusor muscle, which means that L-arginine/nitric oxide pathway may be present in the mechanism of relaxation. Therefore, new therapeutic approach using exogenous nitric oxide will be an attractive modality in treating functional voiding disturbances such as detrusor hyperreflexia and bladder instability.