Functional alterations of cardiac subcellular structures during energy deficiency in relation to the metabolic state of the heart muscle cell.

The functional behaviour of membrane systems of the cardiac cell during oxygen deficiency was analyzed and the alterations were related to the metabolic state of the tissue as an index of injury. 1. The retention function of the cell membrane for proteins. With increasing energy deficiency the cardiac sarcolemma loses its ability to retain macromolecules (myoglobin, enzymes) within the cell. Close correlations exist between protein release and oxygen supply as well as ATP content of the tissue. 2. Function of isolated mitochondria after ischemia. In parallel with a strong impairment of oxidative phosphorylation (decrease of QO2, RCI values, phosphorylation rates) the Ca++-transporting activity of mitochondria is continuously depressed with decreasing myocardial ATP. 3. Function of isolated sarcoplasmic reticulum after ischemia. With breakdown of high energy phosphates during ischemia rate and extent of Ca++ binding with decrease markedly.