Abstract
Riboflavin-2^<14>C and its tetrabutyrate were injected to rats and the excretion of riboflavin into urine was studied. In the case of riboflavin-2^<14>C injection (400μg. total counts 2.19×10^5cpm), 301.6μg (total counts 4.89×1.0^4 cpm) of riboflavin was excreted into urine during 24 hours after the injection. In the case of riboflavin tetrabutyrate-2^<14>C injection (400μg, total counts 2.19×10^5cpm), only 182.0μg (total counts 1.74×10^4cpm) of riboflavin was excreted into urine during 72 hours after the injection. These results confirmed the previously reported fact that riboflavin-^<14>C moiety of riboflavin tetrabutyrate-^<14>C is effectively incorporated into FAD and FMN of organs and stayed in animal body for a long time.
