Effect of hyperosmolarity on both receptor-mediated and fluid-phase endocytosis in ethanol-fed animals

Carol A. Casey, Robert L. Wiegert, Dean J. Tuma

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

We have shown previously that chronic ethanol administration impairs hepatic receptor-mediated endocytosis (RME) of asialoorosomucoid (ASOR), epidermal growth factor and insulin, whereas early uptake by fluid-phase endocytosis (FPE) of a fluorescent dye, Lucifer Yellow (LY), is not altered. Results of these studies suggested that ethanol-induced injury was primarily affecting endocytosis in coated pit areas of the plasma membrane while internalization in noncoated membrane areas was unaffected. In the present study, we investigated the effects of blocking clathrin-coated pit mediated endocytosis by hyperosmolarity on FPE of LY and on RME of ASOR. We also examined the effects of hyperosmolarity on the binding and internalization of insulin, a ligand endocytosed by both RME and FPE. Uptake of LY by noncoated regions of the membrane was not altered in control animals, whereas in hepatocytes from ethanol-fed animals uptake of LY was decreased by 35-40% in the presence of 0.12 M sucrose (P < 0.05). These hyperosmolar conditions almost completely inhibited (> 85%) the endocytosis of 125I-ASOR by RME in both ethanol and control cells. Results with insulin showed slight effects (20-30% impairment) on uptake of the ligand in the presence of sucrose. These results are consistent with previous reports that in normal cells the coated pit pathway is impaired by hyperosmolarity, whereas endocytosis in noncoated regions is unaltered. It appears, however, that both FPE and RME in hepatocytes from ethanol-fed animals are susceptible to perturbation by hyperosmolarity. These results indicate that the noncoated pit pathway may be sensitive to stressful conditions such as hyperosmolarity after ethanol treatment.

Original languageEnglish (US)
Pages (from-to)1117-1123
Number of pages7
JournalBiochemical Pharmacology
Volume49
Issue number8
DOIs
StatePublished - Apr 18 1995

Keywords

  • alcohol
  • fluid-phase endocytosis
  • hepatocytes
  • hyperosmolarity
  • liver
  • receptor-mediated endocytosis

ASJC Scopus subject areas

  • Biochemistry
  • Pharmacology

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