Abstract
Parathyroid hormone (PTH) is regulated by such divalent cations as calcium ion (Ca++) and magnesium ion (Mg++), via adenylate cyclase (AC)-cyclic AMP system at least in part. Since the effects of various divalent cations on PTH secretion have never been compared in details, effects of various divalent cations on PTH secretion from and AC activity in bovine parathyroid cells in simultaneous experiments.
It was observed that Ca++ has suppressive action on PTH secretion and AC activity, while Mg++ and Mn++ have biphasic suppressive effect. The set-point of Ca++ for PTH secretion was 0.8mM and those for Mg++ and Mn++ were 1.0mM and 0.75mM, respectively. The set-points of Ca++ Mg++ and Mn++ on AC activity were 0.8mM, 1.0mM and 1.0mM, respectively.
In view of the recent suggestion that the parathyroid disorder such as hyperparathyroidism represents an abnormality in the set-points of the parathyroid cells for metal ions, the measurement of set-points for divalent cations might provide a useful approach in study of the pathophysiology of parathyroid disorders.
