Glucocorticoid-induced atrophy in different fibre types of selected rat jaw and hind-limb muscles.

Six weeks of glucocorticoid treatment (triamcinolone-acetonide-21-phosphate, 1 mg/kg of body weight daily) resulted in a similar pattern of fibre type atrophy in jaw and hind-limb muscles. Fast-twitch glycolytic fibres were significantly atrophied in all muscles investigated. Fast-twitch oxidative glycolytic fibres were affected only in the fast (white) regions of the mixed muscles, while slow-twitch oxidative fibres were unaffected. The results from pair-fed controls (food intake matched to the glucocorticoid-treated animals) showed that the glucocorticoid produced an atrophic response in addition to that produced by the decreased food intake in the experimental animals. These results suggest that the jaw musculature shares the wasting effects induced by elevated circulating glucocorticoid levels often found in stress situations.