Calcitonin decreases corticosterone-induced skeletal muscle calpain activity

The effects of calcitonin (CT) administration on calcium (Ca) concentrations in plasma and skeletal muscle as well as the calpain activity of skeletal muscle were examined in young growing male rats treated with corticosterone (CTC). The rats received subcutaneous injections of CTC (5 mg/100 g body weight/day), or both CTC and CT (100 m unit/100 g body weight/day) for four days. Control rats received placebos. The rats were sacrificed 24 h after the final injections, and blood was taken followed by dissections to remove gastrocnemius and extensor digitorum longus muscles. Plasma Ca concentration was increased and muscle Ca concentration and its calpain activity tended to be increased by CTC. The CTC-induced increases in muscle Ca concentration and its calpain activity were significantly minimized by the simultaneous injection of CT. However, CTC-induced hypercalcemia was not minimized by CT. The present observations indicate that CT decreases Ca concentration in skeletal muscle cell and its calpain activity, followed by a suppression of muscle proteolysis in rats treated with CTC.