Myocardial function and subcellular calcium metabolism in chronic potassium deficiency.

: Myocardial contractility was examined in whole, perfused hearts and in right ventricle papillary muscles of chronic K-depleted cats. Mitochondrial and sarcoplasmic reticulum (SR) calcium binding and concentration were estimated in the perfused hearts after exposure to 45Ca. In vitro SR Ca uptake was measured by the Millipore technique. Myocardial contractility was depressed in chronic potassium depletion and the degree of depression was related to the reduced SR Ca binding. These experiments suggest altered subcellular Ca metabolism as being a mechanism of depressed myocardial contractility in chronic K depletion.