Importance of extracellular Ca²⁺ and intracellular Ca²⁺ release in ethanol-induced contraction of cerebral arterial smooth muscle☆

Abstract 

The present study was designed to investigate the roles of extracellular Ca²⁺ ([Ca²⁺]₀) influx and intracellular free Ca²⁺ ([Ca²⁺]_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 [Ca²⁺]₀ and pretreatment of canine basilar arterial rings with verapamil (an antagonist of voltage-gated Ca²⁺ channels), thapsigargin (a selective antagonist of the sarcoplasmic reticulum Ca²⁺ pump), caffeine plus ryanodine (a specific antagonist of ryanodine-sensitive Ca²⁺ release), or heparin (an inositol 1,4,5,-trisphosphate [InsP₃]-mediated Ca²⁺ release antagonist) markedly attenuated (~50%–80%) ethanol-induced contractions. The absence of [Ca²⁺]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 [Ca²⁺]_i induced by ethanol. Results of the present study suggest to us that both Ca²⁺ influx through voltage-gated Ca²⁺ channels and Ca²⁺ release from intracellular stores (both InsP₃ sensitive and ryanodine sensitive) are required for ethanol-induced contractions of isolated canine basilar arteries.

Keywords:  Canine basilar arteries, Ethanol, Ca²⁺ influx, Intracellular Ca²⁺ release, Stroke, Vasospasm