Characterization of functional P2X 1 receptors in mouse megakaryocytes

Abstract

Introduction Although accumulating evidence within the past 5 years strongly supports the importance of platelet P2X 1 receptors in hemostasis and thrombosis, P2X 1 receptors of platelet and/or its progenitor cell, megakaryocyte, have not been fully characterized. The aim of this study was to electrophysiologically and pharmacologically characterize the functional P2X 1 receptors on mouse megakaryocytes. Materials and methods The currents in response to nucleotides were examined using the patch-clamp whole-cell recording. Results The agonist profile of megakaryocyte P2X 1 receptors was ATP > α,β-methylene ATP > β,γ-methylene ATP. The P2X 1 receptors exhibited substantial monovalent as well as divalent cation permeability and the ratios of Na + to Cs + and Ca 2+ to Cs + permeability were 1 and 2.5, respectively. P2X receptor antagonists except suramin significantly inhibited the P2X 1 responses with an IC 50 values of 0.4 μM for pyridoxal-phosphate-6-azophenyl-2′,4′-disulfonate (PPADS), 0.3 μM for 2′,3′- O-(2,4,6-trinitophenyl)-adenosine 5′-triphosphate (TNP-ATP), 20 μM for reactive blue 2 (RB2), or 160 μM for 8,8′-(carbonylbis(imino-3,1-phenylene carbonylimino)bis(1,3,5-naphthalenetrisulfonic acid) (NF023), respectively. Suramin had no significant effect on the P2X 1 responses. In rat megakaryocytes, suramin similarly had no significant effect on the P2X 1 responses, but abolished the P2Y receptor-mediated responses, indicating that the suramin was active under present experimental condition. Conclusions These results provide the basic properties of mouse megakaryocyte P2X 1 receptors and would be helpful to examine the P2 receptor signaling in platelets and megakaryocytes.