Effects of sodium and temperature on tension in isolated canine coronary artery

The effects of calcium antagonists and prostaglandin E1 on isolated canine coronary arterial tension

The effects of calcium antagonists (nifedipine, nicardipine, diltiazem, and verapamil) and prostaglandin E1 (PGE1) on the tension of isolated canine coronary arterial strips were studied. In a solution containing 20 mEq/L of K+, 127 mEq/L of Na+, the tension was increased by 500-1,000 mg with 4 mEq/L of Ca2+. This increase in tension was suppressed by Ca-antagonists and PGE1 dose-dependently. Nifedipine 10(-5) M, nicardipine 3 x 10(-7) M, diltiazem 3 x 10(-6) M, and verapamil 3 x 10(-6) M completely suppressed the increased tension. The maximal suppression of the tension produced by PGE1 was about 40% at 10(-10) M. In 20 mEq/L K+ solution (0 mEq/L Ca2+, 37 degrees C), the reduction of the Na+ concentrations from 127 mEq/L to 12 mEq/L increased the tension by 50 to 100 mg. This increase in tension was not suppressed by Ca-antagonists or PGE1. In conclusion, this study demonstrated that Ca-antagonists and PGE1 suppressed an increase in the tension caused by Ca2+ but did not suppress an increase in the tension caused by Na+ reduction.

Effects of magnesium on isolated canine coronary arterial tension

The effects of magnesium on the tension of isolated canine coronary arterial strips were studied. In the solution containing K+ of 20 mEq.l(-1), Ca2+ of 4 mEq.l(-1), and Na+ of 127 mEq.l(-1), the tension was 811 +/- 111 mg with Mg2+ of 1 mEq.l(-1), 494 +/- 135 mg with Mg2+ of 10 mEq.l(-1), 272 +/- 126 mg with Mg2+ of 20 mEq.l(-1), -52 +/- 63 mg with Mg2+ of 30 mEq.l(-1), -69 +/- 80 mg with Mg2+ of 40 mEq.l(-1). In the solution containing K+ of 20 mEq.l(-1), Na+ of 12 mEq.l(-1) and Ca2+ of 0 mEq.l(-1), the tension was 102 +/- 22 mg with Mg2+ of 1 mEq.l(-1), 3 +/- 35 mg with Mg2+ of 10 mEq.l(-1), -49 +/- 33 mg with Mg2+ of 20 mEq.l(-1), -59 +/- 49 mg with Mg2+ of 30 mEq.l(-1), -65 +/- 54 mg with Mg2+ of 40 mEq.l(-1). The data demonstrated that Mg2+ above 30 mEq.l(-1) inhibited the increase in tension caused by Ca2+ and Mg2+ above 20 mEq.l(-1) inhibited the increase in tension caused by low Na+ concentration.