P2Y13 receptor is responsible for ADP-mediated degranulation in RBL-2H3 rat mast cells

Extracellular ADP is known to play many important physiological roles In this study we identified the P2Y(13) receptor in a rat mast cell line (RBL-2H3) and explored the functional role of ADP its endogenous agonist ADP induced both intracellular calcium mobilization and release of hexosaminidase (Hex) In an assay of intracellular calcium ADP was 100-fold less potent than and equally efficacious as the P2Y(1) receptor-selective agonist MRS2365 However ADP was more potent and efficacious than MRS2365 in inducing Hex release and in enhancing antigen-induced Hex release ADP-induced intracellular calcium mobilization was blocked by phospholipase C inhibitor U73122 and by P2Y(1) receptor-selective antagonist MRS2500 but not by pertussis toxin (PTX) suggesting a mechanism mediated by the G(q)-coupled P2Y(1) receptor but not P2Y(13) (G(1)-coupled) or P2X receptors ADP-induced Hex release was blocked by PTX and a selective P2Y(13) receptor antagonist MRS2211 but not by MRS2500 or P2Y(1) receptor-specific siRNA suggesting a G(1)-coupled P2Y(13) receptor-related mechanism Measurement of gene expression confirmed high expression of both P2Y(1) and P2Y(13) receptors (in comparison to a previously reported P2Y(14) receptor) in RBL-2H3 cells Thus we demonstrated that ADP-mediated intracellular calcium mobilization and Hex release in RBL-2H3 cells are via P2Y(1) and P2Y(13) receptors respectively Selective antagonists of the P2Y(13) receptor might be novel therapeutic agents for various allergic conditions Published by Elsevier Ltd