Parathyroid hormone and calcitonin: no direct effect on vitamin D3-mediated, intestinal calcium absorptive mechanism.

Embryonic chick duodenum maintained in organ culture responds to vitamin D3 in the culture medium by increased cyclic AMP concentration, de novo synthesis of a specific calcium-binding protein and by increased uptake and transmucosal transport of radiocalcium. The presence of bovine PTH, porcine or salmon calcitonin had no effect on these intestinal responses suggesting that these hormones may have no direct effect on the vitamin D3-mediated, intestinal calcium absorptive mechanism.