DNA hypomethylation during liver cell proliferation induced by a single dose of lead nitrate.

DNA hypomethylation has already been found in regenerating rat liver and in hepatic (pre)malignant lesions when compared to normal non dividing liver. Here we report that extensive hypomethylation of hepatic DNA occurs in mitogen-treated rat liver. This effect can be seen as early as 12 h after metal treatment and parallels the liver dimension changes. Thus the lowering of the DNA 5-methylcytosine content appears to be a properly characteristic of cellular proliferation, independently from being caused by partial hepatectomy, carcinogen treatments or mitogen administration.