Characterization of Ca-Sensing Receptor-Mediated Ca Influx in Microvascular bEND.3 Endothelial Cells.

Ca-sensing receptors (CaSR), activated by elevated concentrations of extracellular Ca, have been known to regulate functions of thyroid cells, neurons, and endothelial cells (EC). In this report, we studied CaSR-mediated Ca influx in mouse cerebral microvascular EC (bEND.3 cells). Cytosolic free Ca concentration and Mn influx were measured by fura-2 microfluorometry. High (3 mM) Ca (CaSR agonist), 3 mM spermine (CaSR agonist), and 10 μM cinacalcet (positive allosteric modulator of CaSR) all triggered Ca influx; however, spermine, unlike high Ca and cinacalcet, did not promote Mn influx and its response was poorly sensitive to SKF 96365, a TRP channel blocker. Consistently, 2-aminoethoxydiphenyl borate and ruthenium red (two other general TRP channel blockers) suppressed Ca influx triggered by cinacalcet and high Ca but not by spermine. Ca influx triggered by high Ca, spermine, and cinacalcet was similarly suppressed by A784168, a potent and selective TRPV1 antagonist. Our results suggest that CaSR activation triggered Ca influx via TRPV1 channels; intriguingly, pharmacological, and permeability properties of such Ca influx depended on the stimulating ligands.