5-Hydroxytryptamine-induced Ca2+ -independent cGMP formation is mediated by nitric oxide in a nitric oxide synthase-independent manner in NG108-15 cells.
A novel pathway of 5-hydroxytryptamine (5-HT)-induced cGMP formation, which does not require Ca2+ and is distinct from the 5-HT, receptor-mediated pathway, is reported to exist in NG108-15 cells. Although the possible involvement of undefined 5-HT receptors and membrane-bound guanylyl cyclase is suggested. the mechanism is not clarified in detail in this Ca2+ -independent cGMP formation. In the present study, we investigated the activation mechanism of guanylyl cyclase activity. 5-HT-induced Ca2+ -independent cGMP formation was not observed in the cell membrane preparation. In intact cells, the 5-HT-induced Ca2+ -independent cGMP formation was inhibited by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide (carboxyPTIO), a nitric oxide (NO)-specific trapper, and by 3,7-bis(dimethylamino)-phenothiazinium chloride (methylene blue), a cytosolic guanylyl cyclase-specific inhibitor, suggesting the involvement of NO and cytosolic guanylyl cyclase. Ca2+ -independent cGMP formation was not inhibited by 1,2-bis(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl)ester (BAPTA-AM), N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), and various arginine-derivative nitric oxide synthase (NOS) inhibitors. Our findings suggest that 5-HT stimulation results in the generation of NO followed by cGMP formation in an NOS-independent manner in NG108-15 cells.
Arima
T
T
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Mizuno
T
T
Ohshima
Y
Y
Kitamura
Y
Y
Segawa
T
T
Nomura
Y
Y
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002478:Cells, Cultured / Q000187:drug effects; D006152:Cyclic GMP / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D009569:Nitric Oxide / Q000494:pharmacology*; D012701:Serotonin / Q000494:pharmacology*
D009569:Nitric Oxide; D012701:Serotonin; D006152:Cyclic GMP; D002118:Calcium