Studies on Carotenoid Metabolism XIII. The Carotenoid Composition of the Blood, Liver and Ovaries of the Rat, Ewe, Cow and Frog

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Abstract
The carotenoid present in minimum quantities in the liver of the rat after the administration of β-carotene has been shown by unequivocal methods to be all-trans-β-carotene. Only traces of carotene and of carotenols were present in the liver of the ewe. No carotenoids were found in the blood or ovaries. On the other hand, large quantities of β-carotene were present in the blood, liver and ovaries of the cow, while small but definite amounts of carotenols were likewise present. The carotene content of the ovaries far exceeded that of the liver. In the case of frogs, definite amounts of β-carotene and carotenols occurred in both the liver and the ovaries. However, no carotene could be detected in the blood. It is suggested that the variation in absorption and deposition of the carotenoids in the tissues as related to the species of the animal may be related to the presence or absence of appropriate protein receptors in the blood and tissues of these animals. Numerous examples of such carotenoid and vitamin A combinations with protein in the blood and tissues are cited in support of this concept.