STUDIES ON THE VITAMIN A REQUIREMENTS OF THE RAT

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Abstract
Expts. based on the depletion times of avitaminosis A rats after administration of given doses of vitamin A are descr. Laparotomy had no appreciable effect on the vitamin A requirements of the rat; these were increased by choledochocolonostomy. The bile was not a channel for the excretion of vitamin A. The livers of choledocho-colonostomized rats did not contain less vitamin A than unoperated rats maintained under the same conditions. The vitamin A requirements of icteric rats did not differ materially from those of normal rats. Although vitamin A, when administered by stomach tube to the icteric rat, was absorbed, the amount was less than in the case of the normal rat. The vitamin A requirements of the rat were, within the limits studied, independent of the age and the body weight but could be increased by administration of thyroxine or desiccated thyroid. In thyroid-ectomized rats, the need for vitamin A decreased. No relationship was found between the vitamin A requirements of the rat and the ovary.