P2X1 and P2X4 receptor currents in mouse macrophages.
OBJECTIVE
Activation of P2X receptors on macrophages is an important stimulus for cytokine release. This study seeks evidence for functional expression of P2X receptors in macrophages that had been only minimally activated.


METHODS
Whole-cell recordings were made from macrophages isolated 2-6 h before by lavage from mouse peritoneum, without further experimental activation. ATP (1-1000 muM) elicited inward currents in all cells (holding potential -60 mV). The properties of this current were compared among cells from wild type, P2X1 (-/-) and P2X4 (-/-) mice.


RESULTS
Immunoreactivity for P2X1 and P2X4 receptors was observed in wild type macrophages but was absent from the respective knock-out mice. In cells from wild type mice, ATP and alpha beta methyleneATP (alpha beta meATP) evoked inward currents rising in 10-30 ms and declining in 100-300 ms: these were blocked by pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS, 10 microM). ATP also elicited a second, smaller ( approximately 10% peak amplitude), more slowly decaying (1-3 s) at concentrations > or =10 microM: this was resistant to PPADS and prolonged by ivermectin. Macrophages from P2X1 (-/-) mice responded to ATP (>100 microM) but not alpha beta meATP: these small currents were prolonged by ivermectin. Macrophages from P2X4 (-/-) mice responded to ATP and alpha beta meATP as cells from wild type mice, except that ATP did not evoke the small, slowly decaying component: these currents were blocked by PPADS.


CONCLUSIONS
Mouse peritoneal macrophages that are minimally activated demonstrate membrane currents in response to ATP and alpha beta meATP that have the predominate features of P2X1 receptors.
Sim
J A
JA
Faculty of Life Sciences, University of Manchester, Manchester, Lancashire, UK. joan.sim@manchester.ac.uk
Park
C-K
CK
Oh
S B
SB
Evans
R J
RJ
North
R A
RA
D000255:Adenosine Triphosphate / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D007559:Ivermectin; D017737:Macrophages, Peritoneal / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058469:Receptors, Purinergic P2X; D058848:Receptors, Purinergic P2X4
C548227:P2rx4 protein, mouse; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; D058848:Receptors, Purinergic P2X4; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate; D007559:Ivermectin; D000255:Adenosine Triphosphate; C002630:alpha,beta-methyleneadenosine 5'-triphosphate