[Effect of ethanol on isometric tone of aorta from guinea pig]

Using aortic strips isolated from guinea pig, effects of ethanol on vascular smooth muscle tone were studied. Low concentrations (5, 50, 100 mM) of ethanol potentiated norepinephrine and serotonin-induced contractions, but not KCl-induced one. Ethanol (100 mM) potentiated calcium-induced contraction in the presence of norepinephrine, but not that in the presence of KCl. Ethanol (100 mM) showed no effects on norepinephrine-induced contraction in the calcium-free medium. Ethanol (100 mM) augmented 45Ca uptake stimulated with norepinephrine, but not that with KCl. Ethanol at the higher concentration of 600 mM by itself induced contraction, which was inhibited by trifluoperazine or in the calcium-free medium, but not by phentolamine, diphenhydramine, methysergide, indomethacin or nifedipine. Ethanol (600 mM) directly increased 45Ca uptake, which was not affected by nifedipine. These findings indicate that the low concentrations of ethanol potentiate receptor-mediated vascular smooth muscle contraction and the higher concentration of ethanol directly contracts it via facilitation of transmembranous calcium influx.