Dietary cholesterol affects Na+-K+ pump function in rabbit cardiac myocytes.
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.
Gray
D F
DF
Department of Cardiology, Royal North Shore Hospital, Sydney, Australia.
Hansen
P S
PS
Doohan
M M
MM
Hool
L C
LC
Rasmussen
H H
HH
D000818:Animals; D002478:Cells, Cultured; D002784:Cholesterol / Q000097:blood; D002791:Cholesterol, Dietary / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009206:Myocardium / Q000201:enzymology*; D010042:Ouabain / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011817:Rabbits; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors
D002791:Cholesterol, Dietary; D010042:Ouabain; D002784:Cholesterol; D000254:Sodium-Potassium-Exchanging ATPase