Vitamin A and carotene

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Abstract
Even when the liver reserves of vit. A were quite low (100 B.U. per gm. by the SbCl3 method) small amts. (5 B.U.) were found in the kidneys, and sometimes in the lungs. When large, but non-toxic, doses (3.5 mgm. daily) of vit. A distillate were given to adult rats, (a) the conc. in the liver rose to extremely high levels (40,000 B.U.), (b) the conc. in the lungs was about that of the liver under normal conditions, (c) the conc. in the kidney remained fairly low (50 B.U.), and (d) that in other organs was extremely low except for surprisingly high values in the suprarenals (up to 2500 B.U.). More massive doses (12-14 mgm. per day) proved toxic to young rats, causing emaciation, hemorrhagic rhinitis, and loss of hair round the mouth. The distribution of vit. A resembled that found in rats given non-toxic doses except that the conc. in the lungs was even higher (1250 B.U. per gm.) while in one rat dying after 33 days a high kidney value (625 B.U. per gm.) was observed. Attempts to induce hypervitaminosis A by feeding carotene failed. On account of its limited solubility in fats only 8 mgm. of the pigment could be given daily. Rats receiving this amt. grew rapidly and remained in perfect health. After 34 days the liver reserve was only moderately high (1250 B. U. per gm.), indicating about 1% absorption, as opposed to 15% in the case of vit. A. Only very small amounts of vitamin were present in the lungs and kidneys, with negative results in all other organs.

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