Journal of Lipid Research, Vol 21, 406-414, Copyright © 1980 by Lipid Research, Inc.
Initial rate of cholesterol esterification association with high density lipoproteins in human plasma
JC Pinon, AM Bridoux and MH Laudat
The enzyme lecithin:cholesterol acyl transferase has been measured both in
total plasma and in the fraction of plasma from which very low and low
density lipoproteins have been removed by ultracentrifugation. The
correlation between the activity of the enzyme and the free cholesterol
concentration was positive in whole plasma and negative in apoB- deficient
plasma. On the other hand, the positive correlation between plasma
triglycerides and cholesterol esterification was not changed by the removal
of apoB-containing lipoproteins. Subjects with the highest levels of high
density lipoprotein cholesterol were found to have the lowest enzyme
activity, but this correlation was disclosed only in apoB- deficient
plasma. This inverse relationship was abolished when the enzyme activity
was measured in the absence of all lipoproteins with a density less than
1.125 g/ml. Cholesterol esterification, when determined after removal of
lipoproteins with a density less than 1.063 g/ml, was negatively correlated
with the in vivo plasma concentration of lipoproteins in the density range
1.063-1.125 g/ml. The same results were obtained in vitro by addition of
increasing amounts of this class of high density lipoproteins either in
total plasma or in the ultracentrifuged fractions of plasma. This provides
further evidence that the lighter density class of high density
lipoproteins inhibits the enzyme reaction under physiological conditions.
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