VITAMIN A AND CAROTENE. I. THE DETERMINATION OF VITAMIN A IN THE BLOOD AND LIVER AS AN INDEX OF VITAMIN A NUTRITION OF THE RAT

Abstract

I. 86 rats, 28 days old, were placed on vit. A-deficient diet; some were given definite supplements at the beginning of the expt., some were given none throughout; the rest were depleted and then divided into groups receiving different amts. of vit. A. Animals were killed at intervals and the vit. A content of the livers and blood detd. according to Kimble''s modification of the method of Dann and Evelyn. Without any vit. A in the diet, its conc. in the blood and liver declined in a parallel manner. Animals receiving 4 I.U. per day showed depletion levels in the blood and liver at approx. the same time as those receiving none; 20 I.U. per day were not sufficient to maintain storage in the liver, but maintained an elevated though sub-normal conc. in the blood. Detns. of vit. A in the blood are an index of the vit. A nutrition of the body in the rat.[long dash]II. Normal blood plasma concs. for carotene and vit. A, detd. by the method of Kimble, were 100 to 368 [gamma] per 100 cc. for carotene and 21.0 to 43.0 [gamma] per 100 cc. for vit. A. The avg. plasma carotene conc. in diabetic patients was significantly higher than in normals, whereas the vit. A concs. were the same. Carotene tolerance curves on 3 normal and 3 diabetic subjects showed no delay in the fall of the carotene concs. in the diabetics after the adm. of 80 mgs. (130,000 I.U.). This may be an indication that the carotenemia of diabetics is not due to failure of conversion to vit. A. When two normal subjects were depleted for 40 days, the plasma carotene concs. fell to subnormal levels but the vit. A concs. were not appreciably changed.