Anoxia-induced changes in composition and permeability of sarcolemmal membranes in rat heart cell cultures

The effects of energy-deprivation on composition and permeability of the sarcolemmal membrane of cardiac cells was studied using monolayer cultures of neonatal rat heart cells incubated in the absence of oxygen and metabolic substrates for 0 to 10 h at 37 degrees C. In the course of anoxia the cells were analysed for cholesterol content, a sarcolemmal sterol, and L-leucyl-naphthylamidase (LNA) activity, a sarcolemmal protein. In addition, sarcolemmal permeability was studied by measuring the efflux of alpha-hydroxybutyrate dehydrogenase (HBDH) activity from the incubated cells. To test whether cholesterol and LNA are indeed markers of sarcolemmal membrane of the heart cells used, sarcolemmal preparations were obtained using an isolation method with cation-coated beads. The results of this study indicate that during anoxia and substrate depletion, changes in sarcolemmal cholesterol content precede sarcolemmal LNA liberation and cytoplasmic HBDH release. It is concluded that energy-deprivation in cardiac cells destroys sarcolemmal structure and function, secondary to the loss of cholesterol.