Stimulatory Effect of Calcitonin on Calcium Excretion into Bile of Thyroparathyroidectomized Rats

Abstract

The effect of calcitonin (CT) on the bile calcium excretion in thyroparathyroidectomized rats has been investigated. A single intraperitoneal injection of calcium (4.0 mg/100 g) markedly increased the bile calcium excretion of sham-operated rats, suggesting that an increase in serum calcium elevates the excretion of calcium into the bile. In thyroparathyroidectomized rats, however, the injection of calcium did not significantly elevate the excretion of calcium into the bile. The bile calcium excretion of thyroparathyroidectomized rats injected with calcium was predominantly potentiated by the administration of CT. CT alone slightly increased the bile calcium excretion in thyroparathyroidectomized rats. In thyroparathyroidectomized rats injected with calcium, there was an increase in bile calcium excretion as early as 30 min after CT administration and the hormone markedly increased the bile calcium excretion even at the lowest dose (40 MRC mu/100 g). These results suggest that CT stimulates the excretion of calcium into the bile through the liver when calcium increases in the serum.