THE EFFECT OF VITAMIN B 12 AND BIOTIN ON THE METABOLISM OF VITAMIN B 12 IN BIOTIN-DEFICIENT RATS.

1. The effect of the administration of vitamin B(12) and biotin on the metabolic pattern of vitamin B(12) in biotin-deficient rats was studied. 2. No significant changes in the absorption and excretion of orally administered [(58)Co]vitamin B(12) were noted either in vitamin B(12)-treated and or in biotin-fed rats. A significant decrease of the uptake of orally given [(58)Co]vitamin B(12) was observed in the liver and kidneys of biotin-treated rats, whereas an increase of uptake in the kidneys of vitamin B(12)-treated rats was noted as compared with biotin-deficient animals. 3. No significant difference in the excretion of radioactivity was noted between biotin deficient and biotin-fed rats when [(58)Co]vitamin B(12) was administered by injection. A small decrease was observed in vitamin B(12)-treated rats. The retention of injected [(58)Co]vitamin B(12) by major organs of biotin-treated rats was lower than that of biotin-deficient rats. A lower content of [(58)Co]vitamin B(12) was also detected in the organs, with the exception of the kidneys, of vitamin B(12)-treated rats. 4. These results are discussed in terms of an interrelationship between biotin and vitamin B(12).