Abstract
Changes in nicotinate concentration in blood and in urine of animals after the injection of riboflavin-2', 3', 4', 5'-tetranicotinate of which nicotinate moieties were uniformly labeled with tritium (B_2-Nic^*) were investigated in comparison with those of animals injected with uniformly labeled nicotinic acid (NiA^*). The rate of excretion of radioactivity into urine of animals injected with B_2-Nic^* was found to be considerably lower than that of animals injected with NiA^*, suggesting that esterified nicotinate was more accumulative in living body than free NiA. B_2-Nic^*, in contrast to NiA^*, showed no temporal change in radioactivity in the early stage after the injection, and showed a potency in keeping blood NiA level higher than the normal for a long time. It, therefore, suggests that this compound could be beneficially used as deposit type of NiA.
