Disuse atrophy of skeletal muscle is associated with an increase in number of glucocorticoid receptors.

Atrophy of muscles due to disuse is similar in form to glucocorticoid atrophy of the general body musculature. Because of this similarity, a hypothesis was formed which attributed the selective muscle atrophy resulting from immobilization to an increase in glucocorticoid sensitivity. As an initial test of this hypothesis, the thermodynamic characteristics of 3H-dexamethasone binding were examined in cytosol prepared from immobilized and contralateral control gastrocnemius muscles. We report here an increase in numbers of glucocorticoid receptors in immobilized muscles relative to contralateral controls, with no change in binding affinity. These findings support the hypothesis that selective muscle atrophy is a result of changes in glucocorticoid sensitivity.