Ccv. the Vitamin a Content of "light White" Casein by Manan Kumar Maitra and Thomas Moore

THE presence of vitamin A in specimens of casein not subjected to treatment for effecting its removal or destruction has been assumed from the early days of research on vitamins. "Light white" casein (sodium caseinate), a form of casein much used in nutritional experiments, was examined as a source of vitamin A for rats by Culhane [1933]. She found that its use as the protein constituent of a basal diet for rats in place of inactivated casein prevented or delayed xerophthalmia and prolonged the survival period. Without further supplements of vitamin A, however, the rats eventually stopped growing and showed signs of deficiency. Culhane calculated that "light white " casein possesses 1/200th of the activity of cod liver oil, and that its inclusion in the diet at the level of 20% was equivalent to a daily dose of 0 05 mg. of carotene. These conclusions would appear to be based on unduly low estimates of the activities of carotene and cod liver oil. As far as we are aware vitamin A has not hitherto been detected in casein by chemical means. The object of the experiments described below has been to confirm the presence of vitamin A by this means, to arrive at a rough approximation of the amount present and to observe whether or not the vitamin is present in any unusual form or state of combination.