Calcium Regulation in Heart Cells

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Abstract
A study was carried out of the interaction of dog heart mitochondria and sarcoplasmic reticulum with Ca2+ bound to troponin or to its Ca2+-binding component (troponin-C). Both organelles are able to release more than 80% of the Ca2+ bound to the 2 proteins. Sarcoplasmic reticulum is only able to do so in the presence of oxalate, whereas mitochondria are also active in the absence of permeant Ca-complexing anions. Ca2+ uptake in heart mitochondria is severely inhibited by Mg2+. The results are discussed with reference to the problem of the control of Ca2+ in heart sarcoplasm.