Store depletion triggers the calcium release-activated calcium current ( I CRAC ) in macrovascular endothelial cells: a comparison with Jurkat and embryonic kidney cell lines

Abstract

In endothelial cells, different types of Ca²⁺ conductances have been described, but none of them has been clearly identified as I _CRAC, the Ca²⁺ release-activated Ca²⁺ current originally described in mast and lymphoma cells. Here we show that in bovine pulmonary artery endothelial cells (CPAE) depletion of intracellular Ca²⁺ stores by inositol 1,4,5-trisphosphate (InsP ₃), Ca²⁺ ionophores and Ca²⁺ pump inhibitors activates a Ca²⁺-selective conductance in the presence of the Ca²⁺ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA). The current shows inward rectification, a highly positive reversal potential and is blocked by micromolar concentrations of La³⁺. The conditions used in studies of endothelial cells were also employed in those of HEK-293, an embryonic kidney cell line commonly used to express putative store-operated channels, and Jurkat cells, the reference cell model. Similar to CPAE, HEK cells also have an I _CRAC-like current. At 0 mV holding potential the estimated current density is –0.1 and –0.2 pA/pF in CPAE and HEK cells respectively, i.e. 15 and 30% of that measured in Jurkat cells. As shown in studies of Jurkat cells, larger Na⁺ currents are detectable in CPAE and HEK cells following store depletion in Ca²⁺- and Mg²⁺-free medium. The current carried by Na⁺ ions is similarly blocked by micromolar La³⁺, is inwardly rectifying and has a positive reversal potential.