J. Biol. Chem., Vol. 259, Issue 13, 8190-8194, Jul, 1984

High density lipoproteins and lecithin dispersions increase the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase by increasing the rate of synthesis and decreasing the rate of degradation of the enzyme

PA Edwards, SF Lan and AM Fogelman

Incubation of rat hepatocytes, prepared from rats fed a normal diet, with either human high density lipoproteins or lecithin dispersions resulted in a dose-and time-dependent increase in the specific activity of 3-hydroxy-3-methylglutaryl-CoA reductase. Incubation of cells with both high density lipoprotein and lecithin dispersions resulted in an additive stimulation of enzymic activity. We used pulse and pulse-chase experiments, followed by immunoprecipitation of the radiolabeled reductase, to demonstrate that high density lipoproteins and lecithin dispersions resulted in increased rates of synthesis and decreased rates of degradation of the reductase. We also demonstrate, by the use of immunoblots, that the increased enzymic activity was paralleled by an equivalent increase in the mass of the reductase. Addition of human low density lipoprotein to rat hepatocytes resulted in a small decrease in both enzymic activity and enzyme synthesis.
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