Calcium handling in porcine coronary endothelial cells by gastrin-17

In porcine coronary artery endothelial cells (PCAEC), gastrin-17 has recently been found to increase nitric oxide (NO) production by the endothelial NO synthase (eNOS) isoform through cholecystokinin 1/2 (CCK1/2) receptors and the involvement of protein kinase A (PKA), PKC and the beta 2-adrenoreceptor-related pathway. As eNOS is the Ca2+ -dependent isoform of the enzyme, we aimed to examine the effects of gastrin-17 on Ca2+ movements. Thus, experiments were performed in Fura-2-acetoxymethyl-ester-loaded PCAEC, where changes of cytosolic Ca2+ ([Ca2+](c)) caused by gastrin-17 were analysed and compared with those of CCK receptors and beta 2-adrenoreceptors agonists/antagonists. In addition, some experiments were performed by stimulating cells with gastrin-17 in the presence or absence of cAMP/PKA activator/inhibitor and of phospholipase C (PLC) and Ca2+ -calmodulin dependent protein kinase II (CaMKII) blockers. The results have shown that gastrin-17 can promote a transient increase in [Ca2+](c) mainly originating from an intracellular pool sensitive to thapsigargin and from the extracellular space. In addition, the response of cells to gastrin-17 was increased by the adenylyl cyclase activator and the beta 2-adrenoreceptor agonists and affected mainly by the CCK2 receptor agonists/antagonists. Moreover, the effects of gastrin-17 were prevented by beta 2-adrenoreceptors and CaMKII blockers and the adenylyl cyclase/PKA and PLC inhibitors. Finally, in PCAEC cultured in Na+ -free medium or loaded with the plasma membrane Ca2+ pump inhibitor, the gastrin-17-evoked Ca2+ transient was long lasting. In conclusion, this study shows thatgastrin-17 affectedintracellular Ca2+ homeostasis in PCAEC by both promoting a discharge of an intracellular pool and by interfering with the operation of store-dependent channels through mainly CCK2 receptors and PKA/PLC- and CaMKII-related signalling downstream of beta 2-adrenoreceptor stimulation.