Self-regulating factor present in culture supernatants of regenerating hepatocytes in adult rats

Abstract

The auto-regulation mechanism of liver regeneration after partial hepatectomy was investigated in rats. Hepatocytes isolated from the individual remnant livers at various times after 70% removal of the liver were cultured, and determination of DNA synthesis of the cultured hepatocytes and collection of culture supernatants were performed. The maximum value of DNA synthesis was observed at 1 day after the operation and then gradually decreased, and the liver weights recovered rapidly during 2-4 days. The culture supernatants harvested from these primary cultured hepatocytes isolated from the rats at 2, 3 and 4 days after the operation suppressed dose-dependently DNA synthesis of hepatocytes which were isolated from normal rats and stimulated by epidermal growth factor (EGF) and insulin in vitro. The supernatants were non-cytotoxic against hepatocytes, and the activity of them was fairly stable for acid and heat treatments but not for proteolytic enzyme. No inhibition of the binding of EGF to the receptors on hepatocytes was observed. Furthermore, the factor showed an inhibitory activity of mitogen-induced DNA synthesis of human peripheral blood lymphocytes in culture. These results suggested that hepatocytes themselves might modulate the process of liver regeneration by secreting a growth inhibitory factor.