Fasting modulates creatine entry into skeletal muscle in the mouse.

[14C]-Creatine entry into skeletal muscle of mice is inhibited by feeding creatine or by fasting. Plasma creatine specific activity after an i.p. injection of [14C]-creatine is decreased by feeding creatine and increased by fasting. These results indicate that creatine enters muscle via a saturable process that is modulated by fasting.