The effect of cholesterol on the accumulation of intracellular calcium.
Cholesterol/egg phosphatidylcholine (PC) liposomes (1:1 or 4:1, M/M), in which the absolute amount of PC was adjusted to be the same, were incubated with cultured bovine arterial smooth muscle cells for up to 8 h at 37 degrees C. The effect of increased cellular cholesterol on the accumulation of intracellular calcium in these cells was studied. The results indicate that the intracellular calcium content, measured by Fura-2/AM, was increased 2.3-fold by incubation with 4:1, cholesterol/PC liposomes. Kinetic analysis using 45Ca2+ indicated that the increased calcium influx was due to increase of pool size, not from a change of rate constant. (Ca2+ + Mg2+)-ATPase activity was decreased by 4:1, cholesterol/PC liposomes. The molar ratio of cholesterol/phospholipids in the cell membranes was directly proportional to that in liposomes. No change in phospholipid composition was noted. We suggest that the accumulation of intracellular calcium was a composite result due to the altering effect of inserted cholesterol on surface area, and to direct interactions between cholesterol and the proteins of the Ca2+ channel and (Ca2+ + Mg2+)-ATPase.
Zhou
Q
Q
Department of Food Science, University of Illinois, Urbana 61801.
Jimi
S
S
Smith
T L
TL
Kummerow
F A
FA
D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D007700:Kinetics; D008081:Liposomes; D008563:Membrane Lipids / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism
D008081:Liposomes; D008563:Membrane Lipids; D010713:Phosphatidylcholines; D010743:Phospholipids; D002784:Cholesterol; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002118:Calcium