Effect of creatine administration on blood urea level and postexercise glycogen repletion in liver and skeletal muscle in rats.

The aim of the present study was to assess the effect of creatinine administration on urea metabolism in sedentary and exercised Wistar rats and also on the rate of glycogen resynthesis in the liver and skeletal muscle of endurance-trained animals after exhausting exercise. Creatine treatment for 7 days significantly increased the concentration of urea in blood plasma of sedentary as well as exercised rats and this effect was also maintained in trained animals 24 h after exhausting swimming. The rate of glycogen resynthesis in the liver and skeletal muscle after glycogen-depleting exercise was not modified by creatine administration.