Observations on the relationship between pteroylglutamic acid and nicotinamide metabolism

Abstract

Incorporation of 0.5% nicotinamide in a pteroylglutamic acid-free purified ration for young albino rats resulted in forced methylation and consequent depletion of liver choline and methionine and in-creased neutral lipids and decreased phospholipids. Pteroyl-glutamic acid deficiency or nicotinamide feeding also resulted in a decrease in liver choline oxidase activity; a similar but somewhat less pronounced effect on liver xanthine oxidase activity was also reflected in correspondingly increased ability of the liver slices for synthesis of the enzyme in vitro. Epinephrine content of the adrenals is significantly decreased in nicotinamide-fed pteroylglutamic acid-deficient animals. The foregoing effects of nicotinamide toxicity are corrected by pteroylglutamic acid (100 /ug/day/rat) and/or 0.5% dietary choline. There is no marked change in liver stores of pantothenic acid or of coenzyme A as a result of pterolyglutamic acid deficiency. However, ingestion of nicotinamide results in somewhat lowered values for both forms of the vitamin in the liver. Choline supplementation increases liver levels of co-enzyme A. The alleviation by pteroylglutamic acid of nicotin-amide toxicity was also shown in studies with aminopterin-fed rats.