Abstract
Incorporation of riboflavin and its tetrabutylate into various organs of mouse and their excretion were invesigated using autoradiography after administration of ^<14>C compounds. Riboflavin-^<14>C administered intragastrically was absorbed rapidly from the intestine and incorporated into various organs. The maximum concentration of ^<14>C in the organs was observed 30min. to 3 hours after administration. Absorbtion of riboflavin butylate-^<14>C from intestinal epithelium, on the contrary, was not so rapid as that of riboflavin and incorporation into various organs was also delayed. The radioactivity once incorporated into the organs remained for a long time and even twelve hours after the administration, many grains were observed in various organs. Riboflavin butylate was also incorporated into brain much more than riboflavin and remained relatively for a long time.
