EGF-induced receptor autophosphorylation in primary hepatocytes isolated from phenobarbitone-treated mice

Phenobarbitone (PB) treatment of mice causes a decrease in the growth facto r responsiveness of hepatocytes. Here, epidermal growth factor receptor (EG FR) expression and receptor autophosphorylation was determined in hepatocyt es isolated from control and PB-treated mice. There was a decrease in the l evel of EGFR expression in hepatocytes isolated from mice following PB admi nistration when compared to controls. EGF caused an approximate 20-fold inc rease of the 170 KD phosphotyrosine band in control hepatocytes, which was inhibited by the EGFR specific tyrosine kinase inhibitor 4,5-dianilinopthal amide. Following PB treatment, the degree of basal receptor phosphorylation (in the absence of EGF) was significantly greater and therefore the fold r ise in EGFR phosphorylation in isolated hepatocytes was lower than in contr ols. However, the overall extent of EGF-induced receptor phosphorylation wa s not diminished in hepatocytes isolated from PH-treated mice. Therefore th e reduction in responsiveness to growth factors seen in hepatocytes ex vivo or the cessation of proliferation observed in vivo following PH administra tion is unlikely to be attributed to a decrease in ligand binding and subse quent receptor autophosphorylation. (C) 1999 Academic Press.