Role of albumin and high-density lipoprotein as endotoxin-binding proteins in rats with acute and chronic alcohol loading.

In the present study, the role of albumin and high-density lipoprotein (HDL) as endotoxin (Et)-binding proteins in chronically alcohol-fed rats was studied. In acute ethanol-loaded rats, the Et clearance in the blood was slightly prolonged, and the amount of albumin and HDL- bound Et in the blood was markedly increased. In chronic ethanol-loaded rats, the Et clearance was significantly faster than that in the control, and HDL-bound Et was increased. In the chronic ethanol-fed rats with an additional 5 g/kg body weight of ethanol load, the Et clearance was much prolonged, and blood tumor necrosis factor and ALT was elevated, when HDL-bound Et was not further increased. Et-binding capacity of total proteins, albumin, and HDL in the hepatocyte culture medium were increased when the Kupffer cells were preincubated in the medium containing ethanol, and the resultant culture supernatant was added to the hepatocyte culture system. In the culture experiment in the chronic ethanol-loaded rats, such increases were not observed. These results suggest that the increase in Et-binding capacity of HDL and albumin may serve as a protective mechanism against Et in chronic ethanol-loaded rats. An addition of high-dose ethanol to these rats may lead to impaired Et binding and inactivation, which may finally result in increased endotoxicity.