The Mechanism of Radiation-Induced Creatinuria. ∗

Summary

Synthesis of creatine in X-irradiated, creatinuric rats was determined from the balance of creatine retained in the body and creatine and creatinine excreted in the urine. The rate of release of creatine from the muscle of irradiated rats was determined in irradiated rats which were injected with labeled creatine several days before exposure. The C¹⁴ activity of urinary creatine and creatinine reflecting the specific activity of “free” and muscle creatine, respectively, was determined before and after exposure. No alterations in rate of creatine synthesis or in its release from muscle were observed after irradiation. In agreement with previous studies, it was therefore concluded that radiation-induced creatinuria results from a failure of the muscle to utilize creatine synthesized at a normal rate.