P2Y-receptor regulates size of endothelial cells in an intracellular Ca2+ dependent manner

The effects of P2 receptor agonists on cell size and intracellular calcium levels, [Ca(2+)](i), was investigated using cultured endothelial cells isolated from the caudal artery of male Wistar rats. Cell size and [Ca(2+)](i) were measured using a phase-contrast and fluorescent confocal microscopic image analyzer and a Calcium Green fluorescence probe. P2Y receptor agonists, 2-methylthio ATP (2meS-ATP), ADP, UTP and ATP decreased the cell size and increased [Ca(2+)](i) in endothelial cells from rat caudal artery. However, alpha,beta-methylene ATP, a P2X receptor agonist, did not induce these responses. The decrease in size and the increase in [Ca(2+)](i), by 2meS-ATP were blocked by PPADS (P2-antagonist), suramin (P2-antagonist), thapsigargin (Ca(2+) pump inhibitor) and U-73122 (phospholipase C inhibitor). The present results show that activation of P2Y receptors, not P2X receptors, induces a decrease in cell size and an increase in [Ca(2+)](i), and the pharmacological properties of these two responses are the same. We concluded that the size of endothelial cells is regulated by P2Y receptors via intracelluar Ca(2+) derived from Ca(2+) stores.