Failure to demonstrate the stimulative effect of calcitonin on cyclic AMP accumulation in avian bone in vitro

The effect of calcitonin on the metabolism of calcium and cyclic AMP in the avian bone was examined in vitro. In the chick embryonic cortical bone, calcitonin affected neither the level of cyclic AMP nor the parathyroid hormone-induced stimulation of calcium release from bone. Also, the level of cyclic AMP in the cortical or medullary bone of Japanese quails was not increased by calcitonin. The medullary bone did not respond to calcitonin either in freshly prepared tissue or in tissue cultured for 48 hr in the absence of calcitonin. The activity of renal adenylate cyclase of Japanese quails was also calcitonin-insensitive. The inability of calcitonin to increase the level of cyclic AMP and to antagonize the parathyroid hormone-induced stimulation of calcium release from bone may account for the lack of hypocalcemic effect of calcitonin in birds as reported by other investigators.