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.
Bibliographical noteFunding Information:
The excellent assistance of Mrs A. Mendeles and Mrs Ch. Cobin is gratefully acknowledged. The authors would like to express special thanks to Dr R. Rahamimoff for his invaluable help in the critical evaluation of the research project and the preparation of the manuscript. This investigation was supported in part by a grant from the United States-Israel Binational Science Foundation and from the Delegation Generale a la Recherche Scientifique et Technique the French Government, and by a grant from the Joint Research Foundation of The Hebrew University and Hadassah to Dr Y. Hasin. Dr 0. Stein and Dr. Y. Stein are Established Investigators of the Ministry of Health.
- Action potential
- Cultured heart cells
- Ion channels
- Membrane cholesterol content
- Membrane permeability
- Slow cardiac fibers