Effect of cholesterol depletion on the electrical activity of rat heart myocytes in culture

The cholesterol content of biological membranes is known to affect their fluidity and their permeability. In the present work we examine the effects of cholesterol depletion on the electrical activity of cultured rat cardiac cells. Electrical activity was recorded with intracellular electrodes in normal and cholesterol-depleted cardiac cells. Cholesterol depletion of 25 to 42% (mean 33%) was obtained by exposure of the cells to high density apolipoprotein-sphingomyelin mixtures. Cholesterol-depleted cells manifested a significantly faster rate of depolarization than control cells; their spontaneous activity was more resistant to [Na⁺] or [Ca²⁺] deprivation, low pH, verapamil and tetrodotoxin. The present findings are consistent with an increase in calcium and sodium influxes during depolarization in cholesterol-depleted rat heart cells. The present findings are consistent with the hypothesis that cholesterol depletion in rat heart cells causes an increase in calcium and sodium influxes during depolarization.