Parathyroid Hormone Interaction with the Oxidative Phosphorylation Chain EFFECT ON ADEnTOSINE TRIPHOSPHATASE ACTIVITY AND THE ADENOSINE

Considerable attention has been given in the past to the action of parathyroid hormone in promoting calcium mobilization and phosphate diuresis (1). In an effort to gain some insight into the mechanism of action of parathyroid hormone at the molecular level, studies on its biochemical action at the subcellular level have been pursued in this laboratory. It has been shown that parathyroid hormone stimulates a vitamin D-dependent release of calcium (2), nonphosphorylative oxidation (3), and the uptake of orthophosphate (4, 5), magnesium (5), sulfate, and arsenate (6) ions by mitochondria. The hormone-stimulated transport of orthophosphate and magnesium ions was shown to be intimately associated with, and dependent upon, the processes of oxidative phosphorylation (5). Because dinitrophenol and Dicumarol, but not oligomycin B, inhibited the hormone-dependent transport of orthophosphate, it was suggested that the hormone-dependent transport reaction interacted with the phosphorylative chain somewhere between the dinitrophenol and the oligomycin inhibition sites. Evidence giving strong support to this interpretation is now available through studies of the effect of parathyroid hormone on adenosine triphosphatase and the adenosine triphosphate-orthophosphate exchange reactions of mitochondria. It is the purpose of this paper to report these experiments.