ATP-induced currents carried through P2X7 receptor in rat myometrial cells.
OBJECTIVE
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.


METHODS
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.


RESULTS
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+).


CONCLUSIONS
P2X7 receptors carry ATP-induced currents in rat myometrial cells.
Department of Obstetrics and Gynecology, Higashihiroshima Medical Center, Higashihiroshima, Japan. miyoshi_hiroshi@hiro-hosp.jp
Hiroshi
H
Miyoshi
Kaoru
K
Yamaoka
Satoshi
S
Urabe
Yoshiki
Y
Kudo
D000255:Adenosine Triphosphate / Q000819:agonists / Q000494:pharmacology*; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004553:Electric Conductivity; D005260:Female; D009215:Myometrium / Q000737:chemistry / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011247:Pregnancy; D058920:Purinergic P2X Receptor Antagonists / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D058848:Receptors, Purinergic P2X4 / Q000235:genetics / Q000502:physiology; D058486:Receptors, Purinergic P2X7 / Q000235:genetics / Q000502:physiology*; D014162:Transfection
D058920:Purinergic P2X Receptor Antagonists; D058848:Receptors, Purinergic P2X4; D058486:Receptors, Purinergic P2X7; D000255:Adenosine Triphosphate