Time course of ethanol-induced impairment in fluid-phase endocytosis in isolated rat hepatocytes.
The time-course effects of long-term ethanol administration on fluid-phase endocytosis were studied in isolated rat hepatocytes. Rats were pair-fed an ethanol-supplemented liquid diet or an isocaloric control diet for 3 days, 1 wk, 2 wk or 5 wk. Hepatocytes were isolated and incubated at 37 degrees C with various concentrations of the fluid-phase marker Lucifer yellow. Net internalization of the marker dye was determined. After as little as 1 wk, ethanol-fed rats demonstrated marked decreases in the net internalization of dye compared with pair-fed controls; these changes persisted throughout 5 wk of feeding. Because net internalization is the balance between uptake into the cells vs. efflux from the cells, these components were examined individually. Early uptake was not significantly decreased by ethanol feeding; however, efflux of preloaded Lucifer yellow from cells from the ethanol-fed animals was markedly faster than efflux from pair-fed controls. This increased efflux was more prominent in the longer preload time (90 min) compared with a shorter preload time (15 min), indicating an alteration in dye distribution among various intracellular pools. These ethanol-induced changes in fluid-phase endocytosis were apparent for 1 wk through 5 wk of feeding and were similar for all Lucifer yellow concentrations examined. These results indicate that the decreased net internalization of Lucifer yellow through fluid-phase endocytosis is mainly a result of an ethanol-induced increase in efflux possibly caused by altered intracellular trafficking rather than by reduction in uptake.
Camacho
K B
KB
Liver Study Unit, Department of Veterans Affairs Medical Center, Omaha, Nebraska 68105.
Casey
C A
CA
Wiegert
R L
RL
Sorrell
M F
MF
Tuma
D J
DJ
D000437:Alcoholism / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D004705:Endocytosis / Q000187:drug effects*; D000431:Ethanol / Q000494:pharmacology*; D005456:Fluorescent Dyes; D007546:Isoquinolines / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008560:Membrane Fluidity / Q000187:drug effects*; D051381:Rats; D013997:Time Factors
D005456:Fluorescent Dyes; D007546:Isoquinolines; D000431:Ethanol; C017475:lucifer yellow