ATP-Induced Currents Carried Through P2X7 Receptor in Rat Myometrial Cells

Abstract

The functional significance of purinergic P2 receptors in the myometrium is unclear. We previously reported the ATP-induced ionic currents in rat myometrial cells, causing uterine contractility. The aim of this study is to determine the main P2X receptors that carry the adenosine triphosphate (ATP)-induced currents. We cloned predominantly expressed P2X7 receptors from rat myometrium and transfected into cultured COS-7 cells. Reconstructed P2X7 receptor currents were characterized using the whole-cell patch clamp method. Extracellular ATP induced currents through P2X7 receptors with effective concentration (EC(50)) of 155 μmol/L, without desensitization. The myometrial P2X7 receptor was permeable to multiple monovalent cations with conductances ranked as K(+)>Cs(+)>Li(+)>Na(+). It was activated by P2X receptor agonists, with effectiveness ranked as 2',3'-O-(4-benzoylbenzoyl)-ATP (Bz-ATP)>>ATP>αβ-methylene ATP (αβ-MeATP)>2-methylthio ATP (2-MeSATP)>uridine triphosphate (UTP)>guanosine triphosphate (GTP)>adenosine diphosphate (ADP). These currents were blocked by selective P2X7 receptor antagonists and extracellular Mg(2+). P2X7 receptors carry ATP-induced currents in rat myometrial cells.