CHRONIC ETHANOL FEEDING ALTERS THE STRUCTURE AND FUNCTION OF THE EPIDERMAL GROWTH-FACTOR RECEPTOR IN RAT STOMACH

We investigated the effect of chronic ethanol feeding on the EGF recep tor in rat stomach. Adult male rats were fed either an isocaloric cont rol or ethanol (EtOH)-containing liquid diet (36% total calories as Et OH) for 4 weeks. EtOH significantly reduced the specific binding of I- 125-EGF to the gastric mucosal membrane (control vs. EtOH, 2.07 +/- 0. 2 vs. 0.94 +/- 0.16 fmol/mg protein; p < 0.01). Scatchard analysis sug gested that the lower binding might be due to the reduction of EGF rec eptor number, and/or the affinity of the high-affinity binding site. W estern blot analysis, using anti-EGF receptor antibody, revealed four immunoreactive protein bands (180, 150, 60, and 50 kDa) in the lectin- purified gastric membrane prepared from both groups. However, the inte nsities of these protein bands in the EtOH-fed animals were 90% lower compared to the controls. Ln the EGF-responsive protein kinase assay, P-32-ATP was incubated with lectin-purified samples in the absence or presence of 1 mu M EGF. EGF stimulated autophosphorylation of the EGF receptor (180 kDa) in stomach from the control groups. but not the EtO H-fed animals. This EtOH-related alteration of the gastric EGF recepto r may be one of the mechanisms underlying the gastric pathology associ ated with alcohol abuse.