Role of nonselective cation channels as Ca2+ entry pathway in endothelin-1-induced contraction and their suppression by nitric oxide.
The present study was carried out to clarify the role of nonselective cation channels as a Ca2+ entry pathway in the contraction and the increase in [Ca2+]i induced by endothelin- in endothelium-denuded rat thoracic aorta rings, and their suppression by nitric oxide (NO). In Ca2+-free medium, the endothelin-1-induced contraction was suppressed to about 20% of control values, although the increase in [Ca2+]i became negligible. The contraction and the increase in [Ca2+]i monitored by fura 2 fluorescence were unaffected by a blocker of L-type voltage-operated Ca2+ channels nifedipine. A blocker of nonselective cation channels 1-[beta-[3-(4-methoxyphenyl)propoxyl]-4-methoxyphenethyl]-1H-imida zole . HCl(SK&F 96365) suppressed the endothelin-1-induced contraction and increase in [Ca2+]i to the level similar to that after removal of extracellular Ca2+. SK&F 96365 had no further effect on the endothelin-1-induced contraction in the absence of extracellular Ca2+. The endothelin-1-induced contraction and increase in [Ca2+]i were abolished by a donor of NO sodium nitroprusside. The effects of another NO donor 3-morpholinosydnonimine (SIN-1) were also tested and yielded essentially similar results to those for sodium nitroprusside on the endothelin-1-induced contraction. Furthermore, the inhibitory effects of sodium nitroprusside could be blocked with a guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ) at 30 microM. These findings suggest that Ca2+ entry through nonselective cation channels but not voltage-operated Ca2+ channels plays a critical role in the endothelin-1-induced increase in [Ca2+]i and the resulting contraction and that inhibition by NO of the endothelin-1-induced contraction is mainly the result of blockade of Ca2+ entry through these channels.
Department of Pharmacology, Kyoto University, Faculty of Medicine, Japan.
X F
XF
Zhang
T
T
Komuro
S
S
Miwa
T
T
Minowa
Y
Y
Iwamuro
Y
Y
Okamoto
H
H
Ninomiya
T
T
Sawamura
T
T
Masaki
D000818:Animals; D001011:Aorta / Q000187:drug effects* / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D019332:Endothelin-1 / Q000494:pharmacology*; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D007473:Ion Channels / Q000378:metabolism*; D017136:Ion Transport; D008297:Male; D008981:Molsidomine / Q000031:analogs & derivatives / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009543:Nifedipine / Q000494:pharmacology; D009569:Nitric Oxide / Q000494:pharmacology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
D002121:Calcium Channel Blockers; D019332:Endothelin-1; D007093:Imidazoles; D007473:Ion Channels; D020030:Nitric Oxide Donors; D009599:Nitroprusside; D009569:Nitric Oxide; C002385:linsidomine; D008981:Molsidomine; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D009543:Nifedipine; D002118:Calcium