Intravesical oxyhemoglobin initiates bladder overactivity in conscious, normal rats

Purpose: To investigate whether intravesical oxyhemoglobin, a nitric oxide scavenger, changes bladder activity in normal rats. Materials and Methods: Oxyhemoglobin was given intravesically at different concentrations to conscious, female Sprague-Dawley rats undergoing continuo us cystometry. Results: Intravesical oxyhemoglobin increased bladder activity in a concent ration-dependent way. At, a concentration of 2.5 x 10(-4) M (n = 8), mictur ition pressure (p <0.01), basal pressure (p <0.01), and residual volume (p <0.05) increased, and bladder capacity (p <0.001) and micturition volume (p <0.001) decreased. The effect of oxyhemoglobin was reduced or abolished by L-arginine (200 mg./kg.(-1)), given intra-arterially near the bladder, and was enhanced by the guanylate cyclase inhibitor, ODQ (0.5 and 1 mg./kg.(-1 )). The K+ channel opener, ZD6169 100 ng.ml.(-1), given intravesically for 1 hour prior to instillation of oxyhemoglobin, reduced or completely preven ted the bladder activity induced by oxyhemoglobin. Conclusions: Intravesical oxyhemoglobin induces bladder overactivity, proba bly by interfering with nitric oxide (NO) generated in the urothelium or su burothelially. NO may be involved in the regulation of the threshold for af ferent firing in the bladder.