Metabolism and Biological Activity of Vitamin A Acid in the Chick

The amount of vitamin A acid required to prevent vitamin A deficiency symptoms in chicks depended upon the time dosing began relative to the onset of symptoms. The acid was found to have a sparing action on vitamin A in the body. When vitamin A acid was the only source of the vitamin in the diet, chicks grew and developed normally during a 6-week experimental period. When the acid was given in daily oral doses, amounts up to 100 µg would not completely prevent development of ocular or central nervous system lesions, although growth was normal. When a large oral dose was given, the unchanged vitamin A acid could be detected in the tissues up to 18 hours, but not after this time. No other form of vitamin A was detected. The acid was found to be concentrated primarily in the microsomal fraction of liver. Experiments with C14 vitamin A acid confirmed the rapid metabolism or destruction which begins in the digestive tract. Four radioactive fractions, based on solubility, were prepared from chicken liver after a dose of C14 vitamin A acid. Two of these represented the unchanged acid while a third fraction, fat soluble, gave no reaction with antimony trichloride. A fourth fraction was water soluble. In a rat curative assay, the third fraction had biological activity but fraction 4 did not. No evidence was obtained for the conversion in the body of vitamin A acid to the aldehyde or alcohol.