THE EFFECT OF α-TOCOPHEROL ON THE UTILIZATION OF CAROTENE BY THE RAT

In a previous study it was demonstrated that the ingestion of carotene by rats fed thiourea or thiouracil resulted in only negligible stores of vitamin A in the animal, but that normal stores accumulated when the effects of these drugs were corrected with thyroxine (1).The metabolic stimulants and depressants exerted only slight effects on vitamin A storage when the dietary source of the stored vitamin was vitamin A itself rather than carotene.These studies have now been extended to include another factor capable of influencing the rate of biological oxidations, viz.a-tocopherol.The sparing effect of tocopherol on vitamin A and carotene in vivo was first described by Moore (2, 3), and the original observations were greatly amplified by Hickman and his associates (4-6).The latter workers observed, however, that, when a relatively large amount of tocopherol (5 mg. per rat daily) was fed to rats, growth due to carotene or vitamin A was less than when moderate amounts of tocopherol were fed.The effect was greater when carotene was fed.This suggested that tocopherol, like thiourea or thiouracil, might be capable of interfering with the conversion of carotene to vitamin A. In the present study relatively large amounts of tocopherol were administered to rats in various ways, and the storage of vitamin A was determined in rats fed either vitamin A itself or p-carotene.In addition attempts were made to associate differences in storage with the metabolic rate or the fecal excretion of carotene. MethodsWeanling rats were placed on a diet low in vitamin A, consisting of casein 18, dextrin 65, cottonseed (Wesson) oil 5, brewers' yeast 8, and salts 4 (7).16 drops of Drisdoll containing 4000 units of vitamin D were added per 10