1995 Volume 41 Issue 5 Pages 545-552
Two-experiments were conducted to clarify the effect of calcitonin (CT) on growth, muscle protein breakdown, plasma corticos-terone (CTC) concentration and urinary calcium excretion in young growing rats treated with CTC. Rats received hormonal treatments for 6 days (Experiment 1) or 24h (Experiment 2). Dose levels of CTC were 10mg and 5mg/ 100g body weight/day in experiment 1 and 2, respectively, and that of CT was 100m unit/100g body weight/day in both experiments. Muscle protein degradation was evaluated by urinary Nτ methylhistidine excretion. CT increased 24-h urinary calcium excretion but not 6-day calcium excretion. CTC markedly inhibited growth, accelerated muscle protein degradation and increased calcium excretion in both experiments. However, very interestingly, CT minimized CTC-induced muscle proteo-lysis, and normalized the CTC-induced decrease in urinary calcium excretion. Furthermore, CT decreased the CTC-induced increase in the plasma CTC concentration. The present observations indicate that CT reduces CTC-induced muscle protein breakdown by reducing the plasma CTC concentration and that increased urinary calcium excretion due to CT treatment may also play a role in reducing CTC-induced muscle protein breakdown.