vitamin-a2 and 3-hydroxyretinol

1. The metabolism of dehydroretinyl ester has been studied in vitamin-A-deficient white leghorn chicks. Dehydroretinyl ester was metabolized to 3-hydroxyretinol diester, 3-hydroxyanhydroretinol and rehydrovitamin A2 which were isolated from the intestines and livers of chicks. 2. The metabolism of 3-hydroxyretinol diester and 3-hydroxyanhydroretinol, which were immediate metabolites of dehydroretinol, was studied in chicks. 3. Retinol was not detected in these experiments.

Topics: Absorption; Animals; Animals, Newborn; Chickens; Esters; Liver; Reference Values; Vitamin A; Vitamin A Deficiency

In search of other provitamins A, the metabolism of cryptoxanthin was studied in several species of freshwater fish, i.e. Channa gachua, Labeo boga (retinol-rich) and Heteropneustes fossilis (dehydroretinol-rich). The fish were either allowed to starve for 20-25 d to make their intestines free from carotenoids and vitamin A or kept on a vitamin-A-deficient diet for 140-150 d to deplete the initial reserve of vitamin A in the livers. Retinol-rich freshwater fish such as C. gachua and L. boga converted cryptoxanthin into retinol and no 3-dehydroretinol or 3-hydroxyretinol could be isolated from those fish that received cryptoxanthin. 3-Hydroxyretinol and 3-dehydroretinol were isolated from the vitamin-A-deficient H. fossilis, a 3-dehydroretinol-rich freshwater siluroid, after the administration of cryptoxanthin.

Topics: Animals; beta Carotene; Carotenoids; Cryptoxanthins; Fishes; Intestinal Mucosa; Liver; Vitamin A; Vitamin A Deficiency; Xanthophylls