Hypomethylation of hepatic nuclear DNA in rats fed with a carcinogenic methyl-deficient diet.

A progressive decrease was observed in the 5-methyldeoxycytidine content of hepatic DNA in male F344 rats fed with a hepatocarcinogenic methyl-deficient diet. The same dietary regimen resulted in altered hepatic contents of S-adenosylmethionine, the methyl-donating species, and S-adenosylhomocysteine, an inhibitor of DNA methylase. The data indicate that this carcinogenic dietary manipulation is sufficient to alter a possible regulatory process, DNA methylation.