The metabolism of labeled parathyroid hormone. VI. Effects of vitamin D status

Labeled 125I-PTH with full biological activity was utilized to investigate the interrelationship between vitamin D and parathyroid hormone (PTH) function. The distribution of labeled PTH was studied in rats and chickens on diets containing various amounts of vitamin D and calcium. The effects of vitamin D deficiency were found to be minor. There was a slightly delayed (10--30%) blood clearance of the hormone and a smaller deposition in the liver (20--30%) in the D-deficient animals. Deposition in bone and kidney appeared to be essentially normal. It is concluded that any failure of PTH to evoke a bone response in the deficient animal is not due to the failure of binding of hormone at the target organ.