AJP - Heart and Circulatory Physiology, Vol 272, Issue 4 1680-H1689, Copyright © 1997 by American Physiological Society

ARTICLES

Dietary cholesterol affects Na+-K+ pump function in rabbit cardiac myocytes

D. F. Gray, P. S. Hansen, M. M. Doohan, L. C. Hool and H. H. Rasmussen
Department of Cardiology, Royal North Shore Hospital, Sydney, Australia.

Alterations in membrane cholesterol induced in vitro can alter Na+-K+ pump function. Because dietary cholesterol can influence membrane cholesterol in vivo, we examined if dietary cholesterol is a determinant of Na+-K+ pump function. Rabbits were fed cholesterol-supplemented diets for 1-4 wk. Cardiac myocytes were then isolated, and Na+-K+ pump currents (Ip) were measured using the whole cell patch-clamp technique. When the Na+ concentration in the patch pipettes ([Na]pip) was 10 mM, a modest diet-induced increase in serum cholesterol was associated with stimulation of Ip; large increases in serum cholesterol were associated with inhibition. There was no effect of modest or large increases in serum cholesterol on Ip when [Na]pip was 80 mM. The [Na]pip-Ip relationship determined using seven different levels of [Na]pip from 0 to 80 mM indicated that a modest increase in serum cholesterol increased the apparent affinity of the pump for cytoplasmic Na+. In contrast, dietary cholesterol had no effect on the apparent affinity of the pump for extracellular K+. We conclude that cholesterol intake influences the sarcolemmal Na+-K+ pump. This may have clinical implications for cardiovascular function.

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