Effects of nitric oxide on detrusor relaxation

Purpose: Recently we (1994) reported the photo-induced adequate nitric oxide (PIANO) system, in which an NO- or NO₂-carrying molecule which has been photoactivated to release NO, could be exploited to investigate the role of NO in various smooth muscle functions. This study was designed to characterize the effect of nitric oxide (NO) exploiting PIANO on rat detrusor relaxation by isometric tension recording and measuring changes in cGMP content. Materials and Methods: Exposure to ultraviolet light was used (1 to 60 seconds) to evoke PIANO in the presence of streptozotocin, an NO-carrier, and N(ω)-nitro-L-arginine (L-NOARG), an NO₂-carrier. During relaxation the cyclic guanosine monophosphate (cGMP) content was measured by radioimmunoassay. Results: Rat detrusor strips were reversibly relaxed upon NO generation via PIANO. Pyrogallol, an O₂ generator, significantly (p <0.01) diminished PIANO-mediated relaxation. During PIANO-mediated relaxation, the tissue level of cyclic GMP significantly (p <0.05) increased over that of the control. Furthermore, methylene blue, a guanylate cyclase inhibitor, significantly (p <0.01) inhibited both the relaxation and the increase of cGMP. Conclusion: We concluded that rat detrusor muscle was capable of responding to NO, and these findings might lead to a treatment for bladder instability and detrusor hyperreflexia, by the use of intravesical instillation of NO donors.