Abstract
SUMMARY: Treatment of male rats with a single injection of cortisol altered the daily rhythm of weight gain and loss within 12 hr. of the injection, resulting in a net loss of weight after 24 hr. In addition, alterations in skeletal muscle composition and metabolism were studied, especially the changes with time in muscle glycogen content and O2 consumption. Glycogen deposition was detected before the increase in muscle respiration and both effects were maintained when the total amount of muscle steroid had fallen well below the initial value. It is suggested that cortisol has a releasing effect on muscle.