Effects of whole-body x irradiation on the biogenesis of creatine in the rat

Influences of whole-body x irradiation on various aspects of creatine metabolism have been studied. Exposures to sublethal or lethal doses of x radiation results in excessive urinary excretion as well as higher accumulation of creatine in the skeletal muscle of x-irradiated rats. A sudden fall in CPK activity in muscle with a concomitant rise in serum suggests that changes in serum and tissue CPK activity are of an adaptive nature in rats exposed to sublethal doses of x radiation. In vitro studies on creatine synthesis shows that transaminidase and methyl transferase activities in kidneys and liver, respectively, are decreased on the 5th day in the x-irradiated, are decreased on the 5th day in the x-irradiated rat. However, on the 8th day, the enzyme activities are restored to normal