[Effects of cardioplegic solution and calcium entry blockers on coronary artery contraction]

We studied the effects of the electrolyte composition (K, Ca, Na) and calcium entry blockers of the extracellular fluid on the tension development of isolated canine coronary arterial strips. In 20 mEq/l K solution, 4.7 mEq/l calcium produced coronary artery contraction. This Ca-induced contraction was inhibited dose-dependently by calcium entry blockers-nifedipine, nicardipine, diltiazem and verapamil. In the presence of 20 mEq/l K, the reduction of sodium concentration to 12 mEq/l increased the tension of coronary artery. Calcium entry blockers did not affect this tension development. After 5 or 30 min perfusion of calcium entry blockers, Ca-induced contraction was inhibited. It is concluded that low calcium, high sodium cardioplegic solution or addition of calcium entry blockers may relax the canine coronary artery.