Abstract
It was studied, whether the change of riboflavin contents in tissues of the X ray irradiated rat, reported in previous papers were due to a direct effect of irradiation. 1) In rats fed on such a small amount of diet as taken by post irradiated rats, only slight change of the riboflavin distribution in tissues were detected. The marked change of riboflavin contents in various tissues of the irradiated rat seems therefore not to have been caused by fasting, but by the action of irradiation. 2) On the contrary the loss of body weight and the increased riboflavin excretion in irradiated rats seem to be ascribed not to the effect of irradiation, but to fasting, because similar changes were observed in fasting rats. 3) Changes in weight, water content and histological features of tissues of the irradiated rat were, in general, more prominent in the tissues which showed considerable change in riboflavin distribution, but the degree of both change was not parallel. It may therefore be considered that these changes are manifestations of morphological and functional changes induced by the irradiation. 4) From the above results, it may be concluded that the change of riboflavin contents in tissues of the post irradiated rat is a phenomenon characteristic, though not specific, to X ray irradiation, although it may be modified by various other factors.
