Effect of alcohol on lipoprotein metabolism. I. High density lipoprotein binding

The effects of ethanol upon the binding of [125I]-labelled human high density lipoprotein 3 (HDL3) was examined in rat liver microsomes and monolayer cultures of human hepatoma (Hep G2) cells. Alcohol feeding to rats (35% caloric content) caused a significant (p less than 0.05) increase in serum cholesterol concentrations relative to pair-fed controls, but HDL3 binding to rat liver microsomes was unaffected by alcohol consumption. By contrast, addition of 10 mM ethanol to Hep G2 cells increased HDL3 binding, and this increase was observed after 14, 28 and 40 days of exposure. This alcohol-dependent rise in HDL3 binding was associated with a 2.3- to 5-fold rise in receptor number (Bmax), and a 2- to 6-fold increase in the dissociation constant (Kd). The data suggest that the net effect of increased receptor number and lower receptor affinity is to increase the capacity of hepatocytes to metabolize circulating high density lipoproteins, and that this increase in the face of elevated plasma high density lipoprotein cholesterol consequent upon alcohol consumption would facilitate greater mobilization of cholesterol from peripheral tissues to the liver.