Sodium-calcium exchange and sarcolemmal enzymes in ischemic rabbit hearts.
We have investigated alterations in sarcolemmal function that occur during myocardial ischemia. Rabbit ventricles were incubated at 37 degrees C for time periods ranging from 5 min to 2 h. The ischemic tissue was homogenized, and activities of the sarcolemmal enzymes Na+-K+-ATPase, K+-p-nitrophenylphosphatase (K+-pNPPase), and adenylate cyclase were measured in the crude homogenate. Na+-K+-ATPase and K+-pNPPase were substantially inhibited after only 10 min of ischemia, and activities for all three enzymes declined progressively up to 1 h of ischemia, when activities were 37-59% of control. Highly purified sarcolemmal membranes prepared from control tissue and myocardium that had been made ischemic for 1 h showed similar purification of sarcolemmal enzymes, passive Ca2+ binding, and passive permeability to Ca2+. However, the velocity of Na+-Ca2+ exchange in ischemic sarcolemmal vesicles was reduced approximately 50% due to a reduction in Vmax. Although the parallel decline in activities of several sarcolemmal functions might suggest a change in membrane structure, phospholipid and cholesterol contents in ischemic sarcolemma were the same as control.
D009597:4-Nitrophenylphosphatase / Q000378:metabolism; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D003327:Coronary Disease / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D011817:Rabbits; D012508:Sarcolemma / Q000201:enzymology*; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013385:Succinate Dehydrogenase / Q000378:metabolism; D013997:Time Factors
D012964:Sodium; D013385:Succinate Dehydrogenase; D009597:4-Nitrophenylphosphatase; D000262:Adenylyl Cyclases; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium