Importance of extracellular Ca 2+ and intracellular Ca 2+ release in ethanol-induced contraction of cerebral arterial smooth muscle

Abstract

The present study was designed to investigate the roles of extracellular Ca 2+ ([Ca 2+] 0) influx and intracellular free Ca 2+ ([Ca 2+] i) release in ethanol-induced contractions of isolated canine cerebral arteries and primary cultured, cerebral vascular smooth muscle cells. Ethanol (20–200 mM) produced significant contractions in isolated canine basilar arterial rings in a concentration-dependent manner. Removal of [Ca 2+] 0 and pretreatment of canine basilar arterial rings with verapamil (an antagonist of voltage-gated Ca 2+ channels), thapsigargin (a selective antagonist of the sarcoplasmic reticulum Ca 2+ pump), caffeine plus ryanodine (a specific antagonist of ryanodine-sensitive Ca 2+ release), or heparin (an inositol 1,4,5,-trisphosphate [InsP 3]-mediated Ca 2+ release antagonist) markedly attenuated (~50%–80%) ethanol-induced contractions. The absence of [Ca 2+] 0 and preincubation of primary single smooth muscle cells obtained from canine basilar arteries with verapamil, thapsigargin, heparin, or caffeine plus ryanodine markedly attenuated (~50%–80%) the transient and sustained elevations in [Ca 2+] i induced by ethanol. Results of the present study suggest to us that both Ca 2+ influx through voltage-gated Ca 2+ channels and Ca 2+ release from intracellular stores (both InsP 3 sensitive and ryanodine sensitive) are required for ethanol-induced contractions of isolated canine basilar arteries.