EFFECTS OF ETHANOL FEEDING ON THE INTERACTION OF RAT HEPATOCYTES WITHLAMININ PEPTIDES

Laminin, a complex glycoprotein of the extracellular matrix, contains a number of biologically active sites. These sites are involved in cel l growth, attachment, differentiation, and gene expression. Our previo us studies have shown that chronic ethanol consumption by rats impairs hepatocyte attachment to various components of the extracellular matr ix including laminin. In this study, three synthetic peptides (PA22-2, YIGSR, and RGD) that correspond to three distinct functional sites on the laminin molecule were used to investigate the effect of ethanol c onsumption on their cognate receptors. Initially, varying concentratio ns of each peptide were incubated with isolated hepatocytes from ethan ol-fed and pair-fed control rats. These hepatocytes were then assayed for the ability to attach to laminin. The results indicated that air t hree peptides effectively inhibited laminin-mediated cell adhesion: th e degree of inhibition appeared similar between pair-fed controls and ethanol-fed animals. Of the three peptides, PA22-2 showed the most dra matic inhibition of attachment. Therefore, we investigated the ability of hepatocytes to attach directly to PA22-2 Itself. Attachment of hep atocytes from ethanol-fed animals to PA22-2 was impaired by 30% after 4 days and 90% by 14 days. Conversely, no significant difference in at tachment to the entire laminin molecule was observed in ethanol-fed an imate at these early time points. These results indicated that the eth anol-induced impairment of hepatocyte attachment to laminin may be cau sed by the decreased interaction of hepatocytes with specific function al sites on the laminin molecule and that specific receptors on the he patocyte may be affected differently. Because laminin has been shown t o influence cell proliferation, differentiation, and gene expression, this defect could potentially result in structural and functional chan ges of the hepatocytes.