The Use of Isolated Hepatocytes from Rats with Enzyme-altered Foci: Studies of p53 Expression

This paper describes a new version of the widely used technique of isolated rat hepatocyte primary culture. Hepatocytes are isolated from carcinogen-treated rats, and the cultures contain two populations of cells. Data indicate that one cell type derives from enzyme-altered foci (EAF) and one from unaltered tissue. EAF are regarded as precarcinogenic lesions, and the model might be useful in establishing mechanistic and test data for the risk assessment of carcinogens. The two populations differ in their responses to many xenobiotics and toxins. They also differ in their responses to endogenous cell growth control factors. Data are presented on p53 expression in cultured hepatocytes in response to exposure to methyl iodide or diethyl nitrosamine. The responses of the two cell types differed. For example, 0.2mM methyl iodide induced p53 expression in 2–4% of the non-EAF cells, but in less than 1% of the EAF cells. 2% of non–EAF cells and 8% of EAF cells incorporated thymidine. It is concluded that many EAF cells have an attenuated expression of p53 in response to DNA-damaging agents. EAF hepatocytes with damaged DNA may replicate DNA, and this effect could be critical for tumour development.