The Fate of Excess Vitamin A Stores During Depletion

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Abstract
The histologic distribution of the vitamin A fluorescence in the liver was compared with the amount of vitamin A found chemically in liver and blood serum of rats first given large doses of vitamin A, and then placed on a vitamin A free diet. The vitamin A fluorescence ran parallel with the amount of vitamin A found chemically in the liver in all ranges of vitamin A content except when the largest amounts of vitamin were present where the differentiation in the degrees of fluorescence was less clear. This gave additional evidence for the value of the histologic method and recommended it as a simple technic for the estimation of the vitamin A content of organs. No simple parallelism existed between the vitamin A fluorescence of the liver and that of the retina or the blood vitamin A level. Under conditions of large vitamin supply and advanced depletion there was a preponderance of vitamin A in the Kupffer cells over the liver cells. In the middle phase of the depletion period when the amount of vitamin A present compared favorably with that found in adult stock animals, much vitamin A was in the liver cells which probably represent the physiologic storage place. In hypervitaminosis the Kupffer cells store the excess of vitamin A and apparently destroy it; this may explain the uneconomic utilization of vitamin A under conditions of large supply. In depletion the Kupffer cells distribute the remnants of vitamin A. During depletion the livers of male rats lose vitamin A faster than those of females. There is, however, no sex difference with respect to method of utilization, as judged from the histologic picture.