Ethanol feeding selectively impairs the spreading of rat perivenous hepatocytes on extracellular matrix substrates

Background: Hepatocytes require attachment and subsequent spreading on an e xtracellular matrix for their proper growth, function and survival. Our pre vious studies have shown that ethanol feeding selectively impairs perivenul e hepatocyte attachment to various extracellular matrices. This study was u ndertaken to determine whether zonal differences in hepatocyte spreading in response to ethanol feeding occurs and to ascertain the influence of ethan ol consumption on the zonal expression of the beta(1) subunit of integrins, which are the major surface receptors responsible for matrix binding and s ubsequent interactions. Methods: Hepatocytes from the perivenous and periportal regions of the live r were isolated by digitonin/collagenase perfusion from rats that were pair -fed for 2 to 3 weeks with a liquid diet containing either ethanol or isoca loric carbohydrate. The ability of perivenous and periportal hepatocytes to spread on plates coated with either type IV collagen, laminin, fibronectin or polylysine was determined. In addition, the isolated cells were used fo r the analysis of total cellular and surface beta(1) integrin expression. Results: With all of the matrix substrates tested, the spreading of periven ous hepatocytes isolated from the ethanol-fed animals was markedly impaired , while the spreading of periportal hepatocytes was essentially unaffected by ethanol feeding. Both the total cellular as well as the surface expressi on of the beta(1) integrin subunit in perivenous cells from the ethanol-fed rats were significantly higher than from the perivenous control cells, whe reas the total and surface expression of the beta(1) integrin in periportal cells isolated from ethanol-fed and control rats were not significantly di fferent. Conclusions: The results indicated that in addition to impairing hepatocyte attachment, ethanol feeding also impairs another critical step of the adhe sion process, that of hepatocyte spreading on extracellular matrix substrat e. This defect occurred preferentially in perivenous cells and not periport al cells and was associated with an increase in beta(1) integrin expression , suggesting that a compensatory mechanism occurs as an attempt by the peri venous cells to overcome impaired cell-matrix interactions caused by ethano l. Overall, these alterations in extracellular matrix-hepatocyte interactio ns could lead to alterations of hepatocyte structure and function and poten tially play a role in alcoholic liver injury.