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.