NPS-2143 hydrochloride (SB-262470A hydrochloride) stimulates parathyroid hormone (PTH) secretion from bovine parathyroid cells with EC
50
of 41 nM. Moreover, NPS-2143 hydrochloride also blocks the inhibitory effects of calcimimetic NPS R-467 on PTH secretion from bovine parathyroid cells and the inhibitory effects of extracellular Ca2+ on isoproterenol-stimulated increases in cyclic AMP formation.
When infused intravenously in normal rats, NPS-2143 hydrochloride (SB-262470A hydrochloride) causes a rapid and large increase in plasma levels of PTH. Ca
2+
receptor antagonists are termed calcilytics and NPS-2143 is the first substance (either atomic or molecular) shown to possess such activity.
When administered together with an antiresorptive agent (estradiol), NPS 2143 causes an increase in trabecular bone volume and bone mineral density in osteopenic rats.