Journal of Lipid Research, Vol 19, 350-358, Copyright © 1978 by Lipid Research, Inc.
Stimulation of esterified cholesterol accumulation in tissue culture cells exposed to high density lipoproteins enriched in free cholesterol
GH Rothblat, LY Arbogast and EK Ray
Human high density lipoprotein enriched in free cholesterol was obtained by
exposing the lipoprotein to lipid dispersions having a free
cholesterol/lecithin molar ratio greater than two. The metabolism of
cholesterol was studied in tissue culture cells exposed to normal and
cholesterol-enriched lipoproteins. Incubation of Fu5-AH rat hepatoma cells
in medium containing cholesterol-enriched lipoprotein resulted in the
accumulation of cellular cholesterol whereas normal high density
lipoprotein produced no change in cellular content. The accumulated sterol
was recovered primarily as esterified cholesterol and was derived almost
entirely from lipoprotein free cholesterol. The esterification of
incorporated free cholesterol and the cellular cholesterol content were
directly related to the molar ratio of free cholesterol to phospholipid in
the lipoprotein and to the concentration of lipoprotein in the culture
medium. Isotopic experiments utilizing lipoprotein labeled with 125I or
[4-14C]cholesteryl oleate demonstrated that a large fraction of the
cholesterol incorporated from lipoprotein enriched in free cholesterol
occurred by mechanisms that did not result in lipoprotein internalization
and degradation. The response of other tissue culture cells to
cholesterol/phospholipid dispersions is presented. The data indicate that
the lipid composition of a lipoprotein can regulate free cholesterol uptake
and esterification as well as cellular cholesterol content.
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