Crucial roles of nitric oxide synthases in β-adrenoceptor-mediated bladder relaxation in mice

• Published in: American journal of physiology. Renal physiology 2017-01, Vol.312 (1), p.F33-F42
• Main Authors: Satake, Yohei, Satoh, Kimio, Nogi, Masamichi, Omura, Junichi, Godo, Shigeo, Miyata, Satoshi, Saito, Hiroki, Tanaka, Shuhei, Ikumi, Yosuke, Yamashita, Shinichi, Kaiho, Yasuhiro, Tsutsui, Masato, Arai, Yoichi, Shimokawa, Hiroaki
• Format: Article
• Language: English
• Subjects: Animals; Hydrogen Peroxide - metabolism; Isoproterenol - pharmacology; Mice, Transgenic; Muscle, Smooth - metabolism; Nitric Oxide - metabolism; Nitric Oxide Donors - pharmacology; Nitric Oxide Synthase - antagonists & inhibitors; Nitric Oxide Synthase - metabolism; Relaxation - physiology; Urinary Bladder - metabolism; Vasodilation - drug effects
• ISSN: 1931-857X; 1522-1466
• DOI: 10.1152/ajprenal.00137.2016

The specific roles of nitric oxide (NO) synthases (NOSs) in bladder smooth muscle remain to be elucidated. We examined the roles of NOSs in β-adrenoceptor (AR)-mediated bladder relaxation. Male mice (C57BL6) deficient of neuronal NOS [nNOS-knockout (KO)], endothelial NOS (eNOS-KO), neuronal/endothelial NOS (n/eNOS-KO), neuronal/endothelial/inducible NOS (n/e/iNOS-KO), and their controls [wild-type (WT)] were used. Immunohistochemical analysis was performed in the bladder. Then the responses to relaxing agents and the effects of several inhibitors on the relaxing responses were examined in bladder strips precontracted with carbachol. Immunofluorescence staining showed expressions of nNOS and eNOS in the urothelium and smooth muscle of the bladder. Isoproterenol-induced relaxations were significantly reduced in nNOS-KO mice and were further reduced in n/eNOS-KO and n/e/iNOS-KO mice compared with WT mice. The relaxation in n/e/iNOS-KO mice was almost the same as in n/eNOS-KO mice. Inhibition of Ca -activated K (K ) channel with charybdotoxin and apamin abolished isoproterenol-induced bladder relaxation in WT mice. Moreover, direct activation of K channel with NS1619 caused comparable extent of relaxations among WT, nNOS-KO, and n/eNOS-KO mice. In contrast, NONOate (a NO donor) or hydrogen peroxide (H O ) (another possible relaxing factor from eNOS) caused minimal relaxations, and catalase (H O scavenger) had no inhibitory effects on isoproterenol-induced relaxations. These results indicate that both nNOS and eNOS are substantially involved in β-AR-mediated bladder relaxations in a NO- or H O -independent manner through activation of K channels.