title: Expression and functional characterization of P2X receptors in mouse alveolar macrophages.
abstract: Alveolar macrophages (AM) are crucial for pulmonary host defense, and evidence emerges that ATP-gated P2X receptors are involved in inflammatory processes. This study focuses on the expression and functional characterization of P2X receptors in AM from mouse. In RT-PCR experiments, transcripts encoding the P2X₁, P2X₃, P2X₄, P2X₅, and P2X₇ receptors were detected. In whole-cell patch-clamp recordings, ATP (1 mM) evoked an inward current (mouse and human AM) that was reversible upon washout, and the reversal potential was ~5 mV, indicating the activation of a non-selective conductance-a fingerprint of P2X receptors. Further characterization (mouse AM) revealed that the current was not desensitized by a second ATP application. The ATP-induced current was increased by the removal of extracellular Ca²⁺ (in human and mouse AM), and EC₅₀ in mouse AM were determined with ~1 mM ATP, in the presence as well as in the absence of extracellular Ca²⁺. Pharmacological characterization of mouse AM revealed that the effect was augmented by BzATP and pre-application with ivermectin, but no effect with α,β-meATP was observed. Further, the ATP effect was reduced by PPADS (300 μM), brilliant blue G (5 μM), and about A438079 (10 μM). Although different P2X receptor transcripts were detected in mouse AM, the observed functional and pharmacological characteristics indicate primarily the participation of P2X₄ and P2X₇ receptors as mediators of the ATP-induced ion current in mouse AM. These suggestions were confirmed by experiments with AM from P2X₇ -deficient animals, indicating a contribution of P2X₄ and P2X₇ receptors in pulmonary immune function.
authors.affiliation: Institute of Animal Physiology, Justus-Liebig-University Giessen, Giessen, Germany.
authors.forename: Sarah
authors.initials: S
authors.lastname: Kessler
authors.forename: Wolfgang G
authors.initials: WG
authors.lastname: Clauss
authors.forename: Andreas
authors.initials: A
authors.lastname: Günther
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kummer
authors.forename: Martin
authors.initials: M
authors.lastname: Fronius
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007306:Insecticides / Q000494:pharmacology; D007559:Ivermectin / Q000494:pharmacology; D016676:Macrophages, Alveolar / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D018408:Patch-Clamp Techniques; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D058469:Receptors, Purinergic P2X / Q000235:genetics / Q000378:metabolism*
chemical_list: D007306:Insecticides; D020033:Protein Isoforms; D058469:Receptors, Purinergic P2X; D007559:Ivermectin; D000255:Adenosine Triphosphate; D002118:Calcium