Action of Parathyroid Extract on Bone Phosphorus and Calcium in the Rat.

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Abstract
Effect of parathyroid extract upon removal of Ca and phosphate from the long bones of rats was studied by the use of radio-Ca and radio-P. Autoradiographs showed that significant amts. of both phosphate and Ca could be removed from the subepiphyseal plate region of the long bones of rats by parathyroid extract admn.; the amt. of radio-P removed was greater than the radio-Ca. These expts. indicate further that parathyroids act directly on bone to produce this removal of Ca and phosphate, and that this effect is enhanced by an additional effect on the kidney whereby the excretion of phosphate is increased. This assumption is based on the fact that serum phosphate values, which are initially reduced by parathyroid extract, can be raised above normal by extended treatment of the extract. This increase in serum phosphate levels was accomplished while kidney excretion of phosphate was still approx. 10 times the normal daily output, indicating that phosphate was entering the blood at a faster rate than its withdrawal, presumably primarily from the bone.