Abstract
Gamma ray irradiation from Co^<60> was conducted to the whole body of albino rat in order to elucidate the effects of the ionizing radiation upon the riboflavin contents of various body parts of the animal fed daily with a diet containing 25 μg of the vitamin. The animals were divided into three groups. On each group, 400,800 or 2000 r of γ-ray was irradiated respectively. The most outstanding feature was found in the spleen. Namely, the absolute amount of the vitamin in the organ was decreased by the irradiation, whereas the amount per unit weight of the organ was increased. In the small intestine both were increased. As far as the absolute amount of riboflavin was concerned, all viscera of the animal showed a decrease or an indifference on the whole with the exception of the small intestine and the lung. The contents of total and esterified riboflavin were both decreased in blood, whereas they were found increased in urine. Total riboflavin in feces was increased, while its ester ratio decreased. The decrease in blood and increase in urine and feces were proportional to intensity of the ray. With the dose of 400r, FAD contents of most viscera was increased, while FMN was reduced and free riboflavin unchanged. On the other hand, with 800r and 2000r decrease of FAD and increase of FMN and free riboflavin was marked. Especially, the increase of free riboflavin in the small intestine was characteristic. The results mentioned above may be explained in the following way. Namely, γ-ray irradiation caused a negative nitrogen balance and consequently liberation of the tissue riboflavin. The liberated riboflavin might be excreted in urine directly or in feces via the liver, the bile duct and the intestine. Increase of free riboflavin in the small intestine and of FMN in the liver and kidney were also observed under a similar experimental condition. Such phenomena were probably caused by an inhibitory effect on the riboflavin phosphorylation.
