The distribution of vitamin A and factor A2. I

Abstract

Fish eyes contain generally 3-7 p.p.m. Vit. A. Goldfish eyes are richer and contain also factor A2 (693 m[mu] band in SbCl3i test and 345-350 m[mu] maximum in the ultraviolet). The rabbit contains 70 p.p.m. Vit. A in the liver; only traces were found elsewhere and no A2. Many spp. of fish contain relatively large amts. of vit. A in their alimentary tracts, especially in the pyloric caeca, although the stomachs yield only traces. Herring pyloric caecal oils may be richer than cod liver oil and the pyloric caeca of trout (Salmofaris and Salmo irideus) may contain more A than the livers. The factor A2 predominates over A and the ratio A2/A is highest in the liver. Perch also contain vit. A and congeners elsewhere than in the liver. The conger eel stores half its vit. A in the liver. The remainder, apart from traces distributed widely, occurs in the body fat and the adipose tissue of the gonads. The alimentary tract of the turbot is relatively rich except for the stomach (6-7 p.p.m.). Two other large fish, spotted ray (Raja maculata) and sunfish (Mola mola), yielded very little vitamin A from any site. Halibut pyloric caeca and intestines yield large amounts of vit. A, some intestinal oils containing 60-70% vit. A esters. Distr. of vit. A in the intestine runs parallel with weight of tissue except in post-absorptive regions. The possibility that vit. A participates in fat exchange or assimilation is considered in relation to published histological studies, and the significance of vit. A in the alimentary tract is discussed in relation to its origin and function. The position concerning vit. A congeners is reviewed with particular reference to A2. The available information suggests that it is a poly-ene alc. akin to, but more unsaturated than, vit. A. The distribution of A2 is consistent with a sharing of at least some of the vit. A functions in fishes generally and in freshwater species especially.