Membrane changes induced by early myocardial ischemia in the dog

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Abstract
Sarcolemmal and mitochondrial phospholipids were extracted from normally perfused and ischemic regions of the dog heart and the composition of these extracts was analyzed. Relatively pure sarcolemmal fraction obtained from myocardium subjected to 3 h of ischemia exhibited a significantly lower concentration of phospholipids than that obtained from normal myocardium. Phosphatidylcholine and phosphatidylethanolamine were reduced by .apprx. 33%. The fatty acid content in the sarcolemmal phospholipid fraction was reduced by .apprx. 30% without any change in the relative composition. In the mitochondrial fraction, the relative phospholipid composition was altered by ischemia; the major components (phosphatidylcholine, phosphatidylethanolamine and cardiolipin) were reduced by .apprx. 15-20%. These biochemical changes were correlated with ultrastructural lesions observed EM. Extensive regional variability and a wide heterogeneity in the extent of ultrastructural damage was evident in the different organelles in a single cell. Ischemic damage, in the early stages, may advance at widely varying rates in different regions. Significant biochemical and structural disorganization evidently occurs during 3 h of ischemia in the myocardium; one of the initiating events may be the activation of sarcolemmal and mitochondrial phospholipases.