Studies on metabolism of vitamin A. 7. Lowered biosynthesis of ascorbic acid in vitamin A-deficient rats

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Abstract
The chloretone-stimulated urinary excretion of ascorbate and its synthesis in vitro from L- [gamma] -gulonolactone by liver microsomes were markedly diminished in vitamin A-deficient rats, as compared with those in corresponding pair-fed normals; at the severe stages of deficiency both urinary excretion and synthesis in vitro of ascorbate were lowered to negligible values. The administration of ascorbate to vitamin A-deficient rats resulted in less pronounced loss in weight, increased longevity and better health, as compared with ascorbate-deprived vitamin A-deficient ones. The liver [rho] -hydroxyphenylpyruvate oxidase of rats was considerably depressed during vitamin A deficiency. The administration of ascorbate partially restored the lowered enzyme activity, and brought to normal the increased concentrations of phenylalanine and tyrosine in the plasma of vitamin A-deficient rats.