Characterization of functional P2X(1) receptors in mouse megakaryocytes.
BACKGROUND
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.


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>alpha,beta-methylene ATP>beta,gamma-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 microM for pyridoxal-phosphate-6-azophenyl-2',4'-disulfonate (PPADS), 0.3 microM for 2',3'-O-(2,4,6-trinitophenyl)-adenosine 5'-triphosphate (TNP-ATP), 20 microM for reactive blue 2 (RB2), or 160 microM 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.
Ikeda
Masahiro
M
Department of Veterinary Pharmacology, Faculty of Agriculture, University of Miyazaki, Gakuenkibanadai-nishi 1-1, Miyazaki 889-2192, Japan.
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D002413:Cations, Divalent / Q000378:metabolism; D002414:Cations, Monovalent / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D017136:Ion Transport / Q000187:drug effects / Q000502:physiology; D008533:Megakaryocytes / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058469:Receptors, Purinergic P2X; D013498:Suramin
D000970:Antineoplastic Agents; D002413:Cations, Divalent; D002414:Cations, Monovalent; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; D013498:Suramin; D000255:Adenosine Triphosphate