Effects of dexamethasone on myocardial cells in the early phase of acute myocardial infarction.

Dexamethasone exerted no significant hemodynamic effect in sham-operated cats or in cats subjected to acute myocardial ischemia. However, the glucoccortcoid did normalize elevated S-T segments toward pre-ischemic values, and prevented much of the increase in plasma CPK activity following coronary artery ligation. Moreover, dexamethasone prevented loss of CPK activity and restricted the loss of lysosomal hydrolase within ischemic myocardial tissue. These data indicate that lysosomal disruption is an early consequence of myocardial ischemia and that treatment with dexamethasone prevents the loss of myocardial lysosomal and cellular enzymes as reflected in normalization of the ECG and plasma CPK activity of ischemic cats. In this way, dexamethasone may act to retard the spread of the developing infarct within the ischemic myocardium.