Divergent action of transforming growth factor beta on DNA synthesis in human foetal liver cells.

Purified human transforming growth factor beta (TGF beta) was found to be a potent inhibitor of DNA synthesis in human foetal hepatocytes. Half-maximal inhibition occurred at 0.5-1 pM and was reversible, with an increase in DNA synthesis within 24 h following removal of TGF beta. By contrast, in the same cultures, 'fibroblast-like' non-hepatocytes retained the ability to synthesize DNA in the presence of up to 200 fold higher doses of TGF beta. This differential response to TGF beta suggests that it may act as an important cell growth regulator in the human foetal liver.