Effects of calcium antagonists on coronary spasm and pulmonary artery contraction in comparison to their antagonistic action against K-strophanthin in isolated guinea pig atria.

The contraction of the potassium depolarized pulmonary artery of the guinea pig was diminished by the calcium antagonists nifedipine, gallopamil, diltiazem, verapamil and prenylamine. The drugs are listed here in order of activity. The uptake of 45Ca of the depolarized pulmonary artery was reduced by nifedipine, verapamil and prenylamine in this order of activity. The depression of the coronary flow of the isolated guinea pig heart, which was brought about by barium chloride, antigenic rabbit serum or vasopressin plus oxytocin was reduced by infusion of prenylamine. The positive inotropic effect of K-strophanthin on the isolated, electrically stimulated left atrium of the guinea pig heart was reduced by gallopamil, verapamil, prenylamine, diltiazem and nifedipine in this order of activity.