The effect of ischemia and reperfusion on sarcolemmal function in perfused canine hearts

The report deals with the effect of ischemia and reperfusion on purified sarcolemma obtained from canine myocardium of perfused supported heart preparations. Perfusion was carried out with a perfluorochemical (FC-43). Ischemia was produced by intermittent total clamping of inflow and outflow followed by release until the decrease in dP/dt max had become stabile. Purity of sarcolemmal vesicles was ascertained with marker enzymes: succinate cytochrome c reductase (for mitochondria), K +-stimulated p-nitrophenylphosphate (K +-pNPPase), (Na +/K +) ATPase and adenylate cyclase (for SL). In addition Na +/Ca 2+-exchange characteristics for SL were determined. Sidedness of vesicles was ascertained by means of adenylate cyclase activity using sarcolemmal preparations treated and untreated with alamethicin. Emplhasis was placed on ATP-dependent Ca 2+ uptake, phosphorylation of sarcolemmal vesicles and yield of SL proteins. Ischemia and reperfusion resulted in a significant reduction in adenylate cyclase activity. This decline was significant following ischemia and reperfusion. The yield of protein recovered from SL vesicles from ischemic-reperfused heart preparations was also significantly decreased. Both initial rate of ATP-dependent Ca 2+ uptake and maximal Ca 2+ uptake fell significantly following ischemia and reperfusion. The initial rate of phosphorylation also dropped significantly. These disturbances in SL Ca 2+ transport following ischemia and reperfusion are probably a part of the general deficit in Ca 2+ translocation.