Formation of vitamin A in a freshwater fish. Isolation of retinoic acid

The intestines of freshly caught Saccobranchus fossilis (a freshwater fish that contains dehydroretinol) became free from carotenoids and from vitamin A when the fish were starved for about 20 days. When beta-carotene was administered to such fish, retinoic acid could be isolated from the intestines after approx. 4h. When lutein was administered to such fish, dehydroretinol and 3-hydroxyretinol could be isolated from the intestines after approx. 5h.