期刊
CANADIAN JOURNAL OF PHYSIOLOGY AND PHARMACOLOGY
卷 86, 期 8, 页码 546-556出版社
NATL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS
DOI: 10.1139/Y08-048
关键词
human vascular smooth muscle; ET-1; ETA receptor; ETB receptor; R-type calcium channel; nuclear calcium; BQ-123; BMS-182874; BQ-788; A-192621
资金
- Canadian Institutes of Health Research (CIHR)
- Heart and Stroke Foundation of Canada
- Fonds de la recherche en sante du Quebec (FRSQ
- Abbott Laboratories, Chicago, Illinois [A-192621]
Our previous work showed that ET-1 induced a concentration-dependent increase of cytosolic Ca2+ ([Ca](c)) and nuclear Ca2+ ([Ca](n)) in human aortic vascular smooth muscle cells (hVSMCs). In the present study, using hVSMCs and 3-dimensional confocal microscopy coupled to the Ca2+ fluorescent probe Fluo-3, we showed that peptidic antagonists of ETA and ETB receptors (BQ-123 (10(-6) mol/L) and BQ-788 (10(-7) mol/L), respectively) prevented, but did not reverse, ET-1-induced sustained increase of [Ca](c) and [Ca](n). In contrast, nonpeptidic antagonists of ETA and ETB (respectively, BMS-182874 (10(-8) -10(-6) mol/L) and A-192621 (10(-7) mol/L)) both prevented and reversed ET-1-induced sustained increase of [Ca](c) and [Ca](n). Furthermore, activation of the ETB receptor alone using the specific agonist IRL-1620 (10(-9) mol/L) induced sustained increases of [Ca]c and [Ca](n), and subsequent administration of ET-1 (10(-7) mol/L) further increased nuclear Ca2+. ET-1-induced increase of [Ca](c) and [Ca](n) was completely blocked by extracellular application of the Ca2+ chelator EGTA. Pretreatment with the G protein inhibitors pertussis toxin (PTX) and cholera toxin (CTX) also prevented the ET-1 response; however, strong membrane depolarization with KCl (30 mmol/L) subsequently induced sustained increase of [Ca](c) and [Ca](n). Pretreatment of hVSMCs with either the PKC activator phorbol-12, 13-dibutyrate or the PKC inhibitor bisindolylmaleimide did not affect ET-1-induced sustained increase of intracellular Ca. These results suggest that both ETA- and ETB-receptor activation contribute to ET-1-induced sustained increase of [Ca](c) and [Ca](n) in hVSMCs. Moreover, in contrast to the peptidic antagonists of ET-1 receptors, the nonpeptidic ETA-receptor antagonist BMS-182874 and the nonpeptidic ETB-receptor antagonist A-192621 were able to reverse the effect of ET-1. Nonpeptidic ETA- and ETB-receptor antagonists may therefore be better pharmacological tools for blocking ET-1-induced sustained increase of intracellular Ca2+ in hVSMCs. Our results also suggest that the ET-1-induced sustained increase of [Ca](c) and [Ca](n) is not mediated via activation of PKC, but via a PTX- and CTX-sensitive G protein calcium influx through the R-type Ca2+ channel.
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