Preservation of myocardial membrane integrity in the early phase of acute myocardial ischemia
Okuda, M.; Lefer, A.M.
Recent Advances in Studies on Cardiac Structure and Metabolism 12: 507-511
1976
ISSN/ISBN: 0363-5872 PMID: 1032005 Document Number: 105848
Myocardial uptake of dexamethasone (Dex) or methylprednisolone (MP) was studied using tritiated tracers in isolated perfused cat hearts during acute myocardial ischemia. Considerable amounts of Dex and MP were incorported into the plasma membranes in control, border-zone, and ischemic myocardium. Lesser amounts were bound to the remaining subcellular organelles. A gradient of the glucocorticoid uptake was observed decreasing from control myocardium to ischemic myocardium in all subcellular fractions. By the first hour of ischemia, the myocardial plasma membranes underwent marked depletion of activity of 5'-nucleotidase, a plasma membrane marker enzyme, indicating early loss of plasma membrane integrity in acute myocardial ischemia. The incorporation of Dex or MP into the plasma membranes resulted in a significant decrease in loww of 5'-nucleotidase activity of the plasma membranes in the border-zone and ischemic myocardium. The data provide direct evidence 1) to support a membrane stabilizing action of glucocorticoids, and 2) to focus on the plasma membranes as a potentially important site of protection during the early phase of acute myocardial ischemia.