Decreased levels of S-adenosylmethionine in the livers of rats fed phenobarbital and DDT.

Chronic feeding of the liver tumour promoters phenobarbital (PB) and 1,1-bis(rho-chlorophenyl)-2,2,2-trichloroethane (DDT) to male weanling rats at levels of 0.05% in the diet for 1, 3 and 5 weeks reduced the hepatic S-adenosylmethionine (AdoMet) contents by approximately 50%. Such reductions were inhibited by the simultaneous feeding of choline chloride and were completely prevented by the dietary administration of methionine. AdoMet levels greater than 100 mug/g liver were noted in rats receiving PB + methionine for 1 week, DDT + methionine for 1 week or methionine alone for 5 weeks. These results are consistent with the hypothesis that the liver tumour promoting activities of PB and DDT may occur in part through a hepatic methyl insufficiency.