Mechanism of suppressive effect of basic cupric acetate on rat liver carcinogenesis by ethionine.

The rate of ethylation of t-RNA in vivo by L-ethionine[ethyl-1-14C] markedly lowered in the liver of rats fed a diet containing copper than that of control. In corporation of the labeled compound into the t-RNA of liver by a single injection. of L-ethionine[ethyl-1-14C] was inhibited as much as 50% by the preceding concurrent administration of copper and ethionine added in the diet to rats. Direct interaction of copper ion with ethylation by ethione in the specific t-RNA of the rat liver was examined as an important biochemical explanation in molecular level for the inhibitory mechanism of copper on rat liver carcinogenesis by ethionine. Profiles of normal t-RNA on methylated albumin-kieselguhr column chromatography revealed three components for leucine, two of which were found at the tube number 40 to 50 and disappeared in the leucyl t-RNA treated with ethionine. The components for leucine that disappeared were normalized in the liver of rats by the concurrent administration of copper.