NPS-2143 (SB 262470A) is a novel potent and selective antagonist of Ca(2+) receptor.

Ca2+ receptor:43 nM

NPS 2143刺激牛甲状旁腺细胞分泌甲状旁腺激素（PTH）,EC50 为41 nM。此外,NPS 2143会阻断拟钙剂NPS R-467对PTH从牛甲状旁腺细胞分泌的抑制作用以及细胞外Ca2+对异丙肾上腺素刺激的环AMP形成增加的抑制作用。表达人Ca2+受体的HEK 293细胞中,NPS 2143阻断Ca2+受体激活诱发的细胞质Ca2+浓度增加,IC50为43 nM。 在短暂表达hCaSRs的HEK-293细胞中,NPS 2143通过有效抑制GSH (数据未显示)和γ-Glu-Val-Gly活性,明显抑制厚味味觉。

在血压正常的大鼠体内,静脉注射NPS 2143（1 mg/kg） 在甲状旁腺存在的情况下显著增加平均动脉血压（MAP）.在大鼠体内,NPS 2143导致血浆PTH水平迅速增加4-5倍,并且血浆Ca 2+水平也瞬时升高.

This clonal cell line, referred to as HEK 293 4.0-7 cells, are used in a high-throughput screening format to detect agonists and allosteric activators of the Ca2+?receptor. Changes in the concentration of cytoplasmic [Ca2+]i provide a quantitative and functional assessment of Ca2+ receptor activity in these cells and the results using this assay parallel those obtained using a homologous expression system of bovine parathyroid cells. On-line continuous measurements of fluorescence in fluo-3- or fura-2-loaded HEK 293 4.0-7 cells are obtained using a custom-built spectrofluorimeter or a fluorescence imaging plate reader instrument. NPS-2143 is incubated with cells for 1 minute before increasing the concentration of extracellular Ca2+?from 1.0 mM to 1.75 mM. NPS-2143 is tested individually at a concentration of 100 μg/mL (20 μM-80 μM) and those causing more than a 40% inhibition of the control response are considered to be biologically active. To determine the potencies (IC50) of NPS-2143 with biological activity, concentration-response curves are obtained and then, as an initial assessment of selectivity, the effects of NPS-2143 on [Ca2+]i evoked by other G protein-coupled receptors are examined at a concentration several times their IC50. Wild-type HEK 293 cells (and HEK 293 4.0-7 cells) express receptors for thrombin, bradykinin, and ATP, which couple to the mobilization of intracellular Ca2+. These responses can be studied to quickly assess any nonselective action of compounds on G protein-coupled receptors. Additional assays for selectivity include HEK 293 cells engineered to express receptors most homologous in sequence and topology to the Ca2+ receptor. These include native or chimeric receptors for various metabotropic glutamate and γ-aminobutyric acid type B receptors (GABABRs).Chimeric receptors are created using partial sequences of metabotropic glutamate receptors and Ca2+?receptors, engineered to couple to activation of phospholipase C and release of intracellular Ca2+?in HEK 293 cells. NPS-2143 lacking pan-activity are then subjected to structural modifications and their potencies and selectivities monitored using these HEK 293 4.0-7 cell assays in an iterative process.