Calcium Shift into Bone: A Calcitonin-Resistant Primary Action of Parathyroid Hormone, Studied in Rats

Abstract

1. Parathyroid hormone (PTH) injected intravenously into rats caused a small rapid uptake of simultaneously administered radioactive calcium into the skeleton.2. This skeletal uptake ofcalcium occurs in many other species, including the monkey and probably man. It appears to be an initiating event in PTH action on bone.3. Although calcitonin prevents PTH-induced bone resorption, it did not affect this early calcium shift.4. This evidence is discussed in connection with the possibility of combining calcitonin with some other agent for the treatment of osteoporosis.

The Effect of Parathyroid Hormone on the Uptake and Release of Calcium by Bone in Tissue Culture

“…One of the most interesting of these biochemical changes has been the immediate uptake of calcium by cells, whether they be HeLa cells (Borle, 1968), kidney cells (Borle, 1970) or bone cells (Parsons et al, 1971). The latter system has been studied in detail by Parsons and his coworkers (Parsons et al, 1971;Parsons & Robinson, 1971;Robinson, Rafferty & Parsons, 1972) who showed that when PTH was injected into rats or dogs there was an immediate hypocalcaemic response which lasted for about 15-20 min; this was followed by the characteristic hypercalcaemic action of the hormone (Rasmussen, Arnaud & Hawker, 1964). From experiments in rats on the uptake of radiocalcium by various tissues after administration of PTH, Parsons & Robinson (1971) concluded that the hypocalcaemia was primarily due to a transient shift of calcium into bone.…”

Some Acute Metabolic Effects of Parathyroid Hormone in Sheep

“…It is now verified that the initial hypocalcaemia following intravenous injection of PTH is caused by the hormone per se. Par sons ), Par sons & Robinson (1971 and Robinson et al (1972) showed that highly purified PTH caused a slight hypocalcaemia in dogs and rats after intravenous injection. Hypocalcaemia lasted for about 15-20 min.…”