Presence of constitutive endothelial nitric oxide synthase immunoreactivity in urothelial cells of hamster proximal urethra

Electrical field stimulation caused frequency-dependent relaxations in prec ontracted strips of hamster proximal urethra, which were attenuated by L-N- G-nitroarginine methyl ester (10(-4) M) and completely blocked by tetrodoto xin (10(-6) M). Strips of hamster urethra devoid of urothelium showed reduc ed relaxant responses to electrical field stimulation which were abolished by L-N-G-nitroarginine methyl eater (10-(4) M). Western blot analysis showe d the presence of a constitutive endothelial nitric oxide synthase in the u rothelial layer, suggesting that urothelium may release nitric oxide in res ponse to electrical field stimulation and that this release is blocked by t etrodotaxin. It is suggested that the urothelium may contribute to relaxati ons of the smooth muscle of hamster urethra produced by nerve stimulation. (C) 1999 Elsevier Science B.V. All rights reserved.