Abstract
The synthesis of vit. A and closely related compounds constitutes a field of investigation engaged in by numerous organic chemists. Once a new product has been prepared, its chemical structure elucidated and its spectrophotometry characteristics established, there remains the question of its biologic potency, for which no rapid methods of determination are available. The biologic assay procedure as given by USP XIV, including a depletion and assay period, requires a minimum of 46 days or a maximum of 73 days for completion. (U.S. Pharmacopoea XIV, p. 790, 1950).
This report offers a method for identifying as well as roughly evaluating the degree of biologic potency in terms of vit. A activity which is—(1) more rapid; (2) more specific; (3) requires no preliminary depletion period or use of specialized diets. This method depends upon the response of the skeletal structures of the young growing animal to excessive intake of vit. A. This response is specific in the sense that no other vitamin or any compound not closely related structurally to vitamin A gives a similar picture. The syndrome of hypervitaminosis A, with its emphasis upon changes in skeletal structures, has been repeatedly reaffirmed ever since its recognition by Collazo and his associates. Its characterization as an acceleration of normal growth sequences in long bones, first suggested by Wolbach and Bessey ( 1 ) was fully described by Wolbach( 2 ). This response is readily recognized histologically in suitably prepared material when high dosage levels are maintained even for short periods of time. If one uses a weanling rat (the test animal that is most convenient and responds with great uniformity at high dosage levels) a tentative diagnosis can be made within 5-6 days, to be confirmed by histological findings in another 10 days, if the material under investigation has a potency in the range of vitamin A.
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