Protein turnover in skeletal muscle tissue from patients with hyperparathyroidism and the effect of calcium in vitro.

Protein synthesis and degradation rates in muscle tissue from hypercalcemic and normocalcemic patients were compared. Both protein synthesis and degradation rates were similar in muscle tissue from patients with hyperparathyroidism and age-matched, normocalcemic patients. When Ca++ concentration in the incubation medium was increased, protein breakdown was stimulated in muscle tissue from normocalcemic and hypercalcemic patients, while protein synthesis was increased only in muscle tissue from hypercalcemic patients. The results indicate that protein turnover in muscle tissue is not affected by varying serum calcium levels, but can be regulated by increased Ca++ concentration in vitro.