Effect of aging on EGF stimulated DNA synthesis and EGF receptor levels in primary cultured rat hepatocytes.

Epidermal growth factor (EGF) stimulated DNA synthesis and EGF receptor levels were examined in primary cultured hepatocytes from 6, 12 and 24 month old rats. EGF stimulated DNA synthesis began after 12h and reached a peak at 48 h. Although no age difference was seen in the time course of DNA synthesis, the magnitude of synthesis at the peak time in 12 and 24 month old rat hepatocytes was reduced approximately 50 and 70%, as compared to that at 6 months. Hepatocyte EGF receptors exhibited no age difference in the equilibrium dissociation constant (Kd) or the density (Bmax). These results indicate that EGF stimulated DNA synthesis in rat hepatocytes declines with age, and that this reduction is not due to decreased receptor density or specific binding affinity.