Cell growth appears to be controlled by positive and negative cell growth regulation. Little is known about the growth regulation of hepatocytes in the cirrhotic liver. Clarifying the responses of hepatocytes obtained from cirrhotic liver to various growth factors and growth inhibitory factors might aid understanding of alterations in growth regulation of the hepatocytes in the cirrhotic liver. We investigated the effects of hepatocyte growth factor, epidermal growth factor, heparin-binding epidermal growth factor-like growth factor, transforming growth factor-β1, interferon-α and interferon-γ on the DNA synthesis of hepatocytes from cirrhotic and normal rats in primary culture. Cirrhosis was induced in male Sprague-Dawley rats by means of oral administration of 0.05% thioacetamide in drinking water for 4 mo. Hepatocytes were isolated by means of an in situ perfusion method, and DNA synthesis was assessed from the amount of DNA-incorporated [H]thymidine. Stimulation of the DNA synthesis of hepatocytes by hepatocyte growth factor, epidermal growth factor and heparin-binding epidermal growth factor-like growth factor was not different between normal and cirrhotic rat liver. Transforming growth factor-β1 inhibited the DNA synthesis of hepatocytes in both. However, the concentration of transforming growth factor-β1 giving a 50% inhibition of DNA synthesis was about two times higher in cirrhotic hepatocytes (0.11 ng/ml) than in normal hepatocytes (0.06 ng/ml). In cirrhotic hepatocytes, the expression of transforming growth factor-β type II receptor gene was about 50% of that in normal hepatocytes. The percent inhibitions of DNA synthesis by 1.25 × 104 U/ml of interferon-α were 51.6% ± 3.2% and 14.1% ± 7.7% in normal and cirrhotic hepatocytes, respectively, by 1.25 × 103 U/ml of interferon-γ 44.8% ± 10.3% and 19.9% ± 3.4%, respectively. These results suggest that inhibitory regulation of cell growth may be impaired in the hepatocytes from cirrhotic liver. (Hepatology 1994;20:1303-1308).