Actions of parathyroid hormone in the vitamin D-deficient dog.

Abstract

Calcium and phosphorus clearance and hydroxyproline excretion were measured in rachitic dogs before parathyroidectomy, after parathyroid-ectomy alone with the administration of parathyroid extract after parathyroidectomy. In the rachitic dogs, serum P was decreased and P clearance was increased, as compared to controls. After parathyroidectomy of the rachitic animals, urinary P and P clearance decreased strikingly, indicating the ability of the renal tubules to conserve P despite vitamin D deficiency. These results also showed that endogenous parathyroid hormone was exerting a tubular effect to decrease P conservation despire a lack of vitamin D, and was responsible for the abnormalities in P metabolism in the rachitic dogs. After parathyroidectomy, serum C fell in 11 of 12 rachitic animals, and it increased with the subsequent administration of parathyroid extract. These changes could not be attributed to changes in urinary Ca and suggested an action of parathyroid hormone on bone. Urinary hydroxproline decreased after parathyroidectomy and increased with the subsequent administration of parathyroid extract, suggesting an action of parathyroid hormone on collagen metabolism in the vitamin D-deficient animals.