Transient response of thyroidectomized pigs to bolus calcium injections and the effect of salmon calcitonin and parathyroid hormone.

The intravenous injection of calcium gluconate (0.11 mM/kg body weight) into conscious thyroidectomized pigs elicits a 30% rise in both ionized and total calcium concentrations of plasma, which return to basal levels within 180 min. The administration of calcitonin (2.5-10 MRC U/kg body weight) reduces this time to 30 to 40 min which is similar to the time obtained in thyroid intact animals. These results suggest that calcitonin may be involved in the fast calcium removal processes and thus in the short-term regulating system of calcium homeostasis. Neither parathyroidectomy nor the administration of parathyroid hormone affected the time for recovery in thyroidectomized pigs, suggesting that the short-term regulation is independent on the parathyroid gland and its hormone.