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

The effects of calcium and temperature on the tension of isolated canine coronary arterial strips were studied. In 20 mEq. l(-1) K solution, the tension was significantly increased from 0 mg with 0 mEq. l(-1) Ca to 33 +/- 18 mg with 0.2 mEq. l(-1) Ca at 37 degrees C, from -40 +/- 18 mg with 0 mEq. l(-1) Ca to -17 +/- 11 mg with 0.2 mEq. l(-1) Ca at 30 degrees C, from -77 +/- 19 mg with 0 mEq. l(-1) Ca to -52 +/- 17 mEq. l(-1) with 1 mEq. l(-1) Ca at 25 degrees C, from -88 +/- 13 mg with 0 mEq. l(-1) Ca to -41 +/- 18 mg with 2 mEq. l(-1) Ca at 20 degrees C, from -125 +/- 16 mg with 0 mEq. l(-1) Ca to -116 +/- 13 mg with 2 mEq. l(-1) Ca at 15 degrees C. Ca higher than 0.2 mEq. l(-1) produced a dose-dependent increase in tension between 37 degrees C and 15 degrees C. In spite of the presence of 4 mEq. l(-1) Ca, the development of tension was strongly supressed by lowering the temperature below 20 degrees C, and completely inhibited at 10 degrees C. The rate of a decrease in tension caused by cooling was about 5.5 mg. degrees C(-1). This study demonstrated that Ca(2+) produced a dose-dependent increase in tension in high-K solution, which was suppressed as the temperature was lowered.