Vitamin A in Adrenal Hormone And Mucopolysaccharide Biosynthesis
Vitamin A deficiency was found to cause an abnormal metabolism of acetate, and reduced glyconeogenesis. This was traced to a malfunction of the adrenal cortex and, ultimately, to an interruption of adrenal glucocorticoid hormone (corticosterone) biosynthesis in the vitamin A deficient rat. In adrenal cortex homogenates from vitamin A deficient animals, the reduced corticosteroid biosynthesis could be restored to normal by adding vitamin A or vitamin A acid in vitro. The influence of the vitamin on one of the enzymes of corticosteroid biosynthesis seems, therefore, to be a direct one.
Another lesion caused by vitamin A deficiency, the degeneration of mucous membranes, was found to be due to a requirement for vitamin A in mucopolysaccharide biosynthesis. This was shown by lowered incorporation of labeled sulfate or glucose into mucopolysaccharide in rat colon homogenates, restorable specifically by added vitamin A. Similarly, net synthesis of mucopolysaccharides in rat colon homogenates, as measured by an increase in mucopolysaccharide-bound hexosamines, is partially dependent on vitamin A. This effect was traced to an enzyme fraction and finally to a single reaction in the biosynthesis of mucopolysaccharide, the activation of sulfate to form adenosine phosphosulfate.