Effect of chronic ethanol administration on total asialoglycoprotein receptor content and intracellular processing of asialoorosomucoid in isolated rat hepatocytes.
Chronic ethanol administration markedly impairs the process of receptor-mediated endocytosis (RME) of a representative asialoglycoprotein, asialoorosomucoid (ASOR), by the liver (Casey et al. (1987) J. Biol. Chem. 262, 2704-2710). Decreased surface binding was the major defect reported in our initial study, along with impaired internalization and degradation of 125I-ASOR in chronically-fed ethanol animals. In this study, we further characterized these impairments by examining the content of intracellular receptors and by investigating ligand processing directed by these intracellular receptors. Ethanol administration for 5-7 weeks decreased intracellular ASOR receptor content by 40%, a result which was confirmed by using both a ligand-binding assay and an antibody-binding assay. In addition to a decreased number of intracellular receptors, an impairment in intracellular processing of receptor-ligand complexes was identified. In ethanol-fed animals, dissociation of receptor-ligand complexes was decreased during steady-state conditions of endocytosis at 37 degrees C. Impaired receptor-ligand dissociation did not alter the fate of the ligand which was to undergo diacytosis (ligand recycling), but did appear to impair degradation of intracellular ligand. These results indicate that chronic ethanol administration decreases ligand binding due to a decreased number of receptors and impairs intracellular processing of ASOR in hepatocytes.
Casey
C A
CA
Liver Study Unit, Veterans Administration Medical Center, Omaha, Nebraska 68105.
Kragskow
S L
SL
Sorrell
M F
MF
Tuma
D J
DJ
D000437:Alcoholism / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D037263:Asialoglycoprotein Receptor; D001212:Asialoglycoproteins; D001692:Biological Transport; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D007700:Kinetics; D008024:Ligands; D008099:Liver / Q000276:immunology / Q000378:metabolism*; D009961:Orosomucoid / Q000031:analogs & derivatives* / Q000378:metabolism; D051381:Rats; D011971:Receptors, Immunologic / Q000378:metabolism*; D012016:Reference Values
D037263:Asialoglycoprotein Receptor; D001212:Asialoglycoproteins; D008024:Ligands; D009961:Orosomucoid; D011971:Receptors, Immunologic; C017030:asialoorosomucoid