Calcitonin and the Formation of 32,52-AMP in Bone and Kidney*

Porcine calcitonin, O.S µg⁄ml; salmon calcitonin, 0.001 µg⁄ml; or parathyroid hormone caused an increase in concentration of 3',5'-AMP in calvaria incubated in vitro. The maximal effects of parathyroid hormone and salmon calcitonin were additive. Propranolol, 20 µM, partially inhibited the effect of salmon calcitonin but not of parathyroid hormone. Adenylate cyclase extracted from calvaria was activated by parathyroid hormone or by 0.001 µg'ml of salmon calcitonin. Maximal effects of parathyroid hormone and calcitonin on adenylate cyclase were additive. The effect of calcitonin was partially inhibited by propranolol, 20 µM. Renal cortical adenylate cyclase was activated by 0.025 µg'ml of porcine calcitonin and 0.001 µg'ml of salmon calcitonin. Salmon calcitonin showed a log-linear dose response from 0.025-0.1 µg'ml and was 20 times more potent than porcine calcitonin as calculated by standard bioassay methods. Propranolol did not inhibit the effect of salmon calcitonin on the renal enzyme.The greater potency of salmon calcitonin over porcine calcitonin in each tissue is commensurate with the ratios of potencies in vivo, and suggests that 3',5'-AMP indeed mediates the physiological response to calcitonin. The additive effects of parathyroid hormone and calcitonin were taken as further evidence that the receptors for parathyroid hormone and calcitonin are distinct. (Endocrinology94: 241, 1974)