[Effect of folic acid deficiency on the synthesis of pteroylpolyglutamates].

In order to evaluate the effect of folate deficiency on pteroylpolyglutamate synthesis in rat liver, the hepatic and urinary content of reduced folates, the distribution of pteroylpolyglutamates and the incorporation of i.p. injected 3H folic acid in polyglutamates have been studied. In deficient rats the hepatic content of reduced folates and the urinary amounts of reduced metabolites are lower and do not increase after vitamin treatment. Longer chain pteroylpolyglutamates are severely depleted and their content is not significantly modified by folic acid treatment. The percentage of labelled folic acid incorporated into pteroylglutamates is markedly decreased. The inability of deficient rat liver to synthesize polyglutamates might be ascribed to the decrease of pteroylpolyglutamate synthetase activity, and/or to the lower availability of tetrahydrofolates, the preferred substrates for the enzyme.