Effect of thyrocalcitonin on calcium concentration in liver of intact and thyroparathyroidectomized rats

Thyrocalcitonin (TCT; 80 MRC mU/100g) administered SC to intact and thyroparathyroidectomized rats, caused a significant decrease in serum calcium, while increasing the liver calcium concentration. The accumulation of calcium in the liver, induced by TCT, was potentiated by the injection of calcium in both intact and thyroparathyroidectomized rats. In thyroparathyroidectomized rats, the administration of imidazole (30 mg/100 g) produced a significant increase in liver calcium and a corresponding fall in serum calcium. The rise in liver calcium produced by TCT was slightly potentiated by prior administration of imidazole, but was not enhanced by prior administration of theophylline (12 mg/100 g) which caused a significant elevation of serum calcium. These results suggest that the action of TCT on liver calcium does not involve cyclic AMP.