Cytochemical localization of lysosomal enzyme activity in normal and ischemic dog myocardium.

The effect of ischemia on the integrity of myocardial lysosomes was observed 3 1/2 and 24 hours after the production of infarcts in 20 anesthetized closed-chest dogs by electrically induced thrombosis of the left anterior descending coronary artery. Biopsies from normal, marginal and infarcted areas were fixed and incubated to localize the lysosomal enzymes acid phosphatase and aryl sulphatase. Reaction product in normal cells was localized in small circular or oblong profiles between bundles of myofilaments and adjacent to mitochondria. In addition, curvilinear, membrane-bound profiles containing reaction product were found in close apposition to transverse tubules and near the free margins of the myocardial cells. Thus the distribution of elements of the sarcoplasmic reticulum. Additional reaction product was also seen in residual bodies, on myelin figures, and in the few conventional appearing spherical lysosomes. Little or no acid phosphatase or aryl sulphatase reaction product was seen in the sarcoplasmic reticulum of infarcted myocardium. The degree of cellular degeneration correlated with disappearance of enzyme activity from the sarcoplasmic reticulum and included disruption of membranes and loss of mitochondrial matrix and erosion of I but not A bands. Marginal areas showed variable amounts of cellular degeneration. Separation of myofilament bundles and loss of glycogen correlated with the localized disappearance of acid phosphatase and aryl sulphatase activity in marginal tissue. Disruption of mitochondrial and erosion of I bands correlated with extensive loss of these enzymes. The data suggest that degeneration of myocardial cells following ischemic injury is associated with release of endogenous lysosomal enzymes from the sarcoplasmic reticulum.