The Influence of Diet upon the Storage of Vitamin B12 in Liver and Kidney

Abstract

Litter mate weanling rats were depleted for two weeks of vitamin B12 and either riboflavin, folic acid or choline. For a 4-week experimental period they were injected with 1.5 µg of vitamin B12 weekly and fed either a diet low in one of the vitamins being studied (0.2 mg riboflavin, or 0.1 mg folic acid or 0.05 gm choline per 100 gm of diet) or the same diet with a high level of the vitamin (1.0 mg riboflavin, 0.5 mg folic acid, or 0.1 gm choline per 100 gm). The vitamin B12 content of the lyophilized livers and kidneys was determined, using the Z strain of E. gracilis with respect to both total and free vitamin. Littermates were continued for the additional 4-week period on the deficient diet. For all three vitamins the deficient rats showed a significantly lower level of both total and free vitamin B12. The dietary increase of riboflavin or of folic acid from low to higher levels resulted in small increases of total and free vitamin B12 in both liver and kidney on a dry weight and on a nitrogen basis. There was evidence of interrelationship. On the high-riboflavin diet the free vitamin B12 increased to 100% in the liver and remained at 80% in the kidney. On the high-folic acid diet the free vitamin B12 remained close to 80% in the liver and 100% in the kidney. While the vitamin B12 content of the low-choline diet approximated those for the two other low diets, the high diet showed a significant decrease which could not be accounted for by possible lesions produced during the depletion period. The free vitamin B12 dropped from 91 to 77% in the liver and remained at 100% in the kidney. The storage of vitamin B12 in liver and kidney was influenced not only by the vitamin B12 content of the diet but by constituents such as riboflavin, folic acid and choline at levels below optimal but sufficiently high to prevent deficiency symptoms.