Epidermal growth factor (EGF) binding, EGF-dependent autophosphorylation and activity of tyrosine-specific protein kinase in hepatic membrane fractions from fetal, newborn, adult and partially hepatectomized rats.

The binding of 125I-epidermal growth factor (EGF) and activities of EGF-receptor autophosphorylation and of tyrosine-specific protein kinases were determined in hepatic membrane fraction from newborn, fetal and hepatectomized adult rats and compared with those of adult control rats. Although the EGF binding was decreased, there was a tendency for the activity of autophosphorylation to be higher and ligand-dependency to be lower in the membranes from growing hepatic tissues. The activity of tyrosine kinases did not differ among animal groups but a supplement of (NH4)2SO4 to the incubation mixture revealed a difference in the EGF-dependency of the activity; the salt inhibited the activity in the control more profoundly than in the newborn and fetus but the activity was partially restored in the presence of EGF, while in the newborn and fetus the activity did not respond to the added EGF. The results suggest that the higher activity with less responsiveness to the ligand of EGF-receptor autophosphorylation and protein-tyrosine kinase is one of the characteristics of growing rat hepatic tissues.