Contraction independent of extracellular Ca by sodium vanadate in guinea-pig vas deferens.

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Abstract Shimada, T. and Sunano, S. <I>Contraction independent of extracellular Ca by sodium vanadate in guinea-pig vas deferens</I>. Japanese Journal of Smooth Muscle Reserach, 1985, 21 (2), 107-117.-The effects of Ca removal and Ca antagonists on sodium vanadate-induced contractions of the guinea-pig vas deferens were studied. Sodium vanadate-induced tension development could be observed even 120 minutes after the removal of Ca, whereas K-contracture disappeared within 20 minutes. Spontaneous contractions induced by sodium vanadate were abolished by the removal of Ca. Verapamil and nifedipine did not show any effect on sodium vanadate-induced contraction, contrastingly, they blocked spontaneous contractions initiated by sodium vanadate. The effects of sodium vanadate on Ca contracture of depolarized prepara-tions were also studied. Though the drug potentiated phasic contraction, it did not potentiate tonic component of Ca contracture.<BR>It was demonstrated that sodium vanadate induced tension development indepen-dently of extracellular Ca, presumably by releasing intracellularly bound Ca.