Dietary cholesterol affects na+-k+ pump function in rabbit cardiac
myocytes.
Gray, David F., Peter S. Hansen, Melissa M. Doohan, Livia C. Hool, and
Helge H. Rasmussen.
Department of Cardiology, Royal North Shore Hospital, Pacific
Highway, St Leonards, 2065, Sydney, Australia
APStracts 3:0492H, 1996.
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 one to four weeks. Cardiac myocytes were then
isolated and Na+-K+ pump currents (Ip) 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 7
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.
Received 18 March 1996; accepted in final form 5 November 1996.
APS Manuscript Number H255-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996