title: Bradykinin acutely inhibits activity of the epithelial Na+ channel in mammalian aldosterone-sensitive distal nephron.
abstract: Activation of the renal kallikrein-kinin system results in natriuresis and diuresis, suggesting its possible role in renal tubular sodium transport regulation. Here, we used patch-clamp electrophysiology to directly assess the effects of bradykinin (BK) on the epithelial Na(+) channel (ENaC) activity in freshly isolated split-opened murine aldosterone-sensitive distal nephrons (ASDNs). BK acutely inhibits ENaC activity by reducing channel open probability (P(o)) in a dose-dependent and reversible manner. Inhibition of B2 receptors with icatibant (HOE-140) abolished BK actions on ENaC. In contrast, activation of B1 receptors with the selective agonist Lys-des-Arg(9)-BK failed to reproduce BK actions on ENaC. This is consistent with B2 receptors playing a critical role in mediating BK signaling to ENaC. BK has little effect on ENaC P(o) when G(q/11) was inhibited with Gp antagonist 2A. Moreover, inhibition of phospholipase C (PLC) with U73122, but not saturation of cellular cAMP levels with the membrane-permeable nonhydrolysable cAMP analog 8-cpt-cAMP, prevents BK actions on ENaC activity. This argues that BK stimulates B2 receptors with subsequent activation of G(q/11)-PLC signaling cascade to acutely inhibit ENaC activity. Activation of BK signaling acutely depletes apical PI(4,5)P(2) levels. However, inhibition of Ca(2+) pump SERCA of the endoplasmic reticulum with thapsigargin does not prevent BK signaling to ENaC. Furthermore, caffeine, while producing a similar rise in [Ca(2+)](i) as in response to BK stimulation, fails to recapitulate BK actions on ENaC. Therefore, we concluded that BK acutely inhibits ENaC P(o) in mammalian ASDN via stimulation of B2 receptors and following depletion of PI(4,5)P(2), but not increases in [Ca(2+)](i).
authors.affiliation: Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, 77030, USA.
authors.forename: Oleg
authors.initials: O
authors.lastname: Zaika
authors.forename: Mykola
authors.initials: M
authors.lastname: Mamenko
authors.forename: Roger G
authors.initials: RG
authors.lastname: O'Neil
authors.forename: Oleh
authors.initials: O
authors.lastname: Pochynyuk
mesh_terms: D000042:Absorption; D000450:Aldosterone / Q000378:metabolism*; D000818:Animals; D015374:Biosensing Techniques; D001920:Bradykinin / Q000494:pharmacology*; D002110:Caffeine / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D062686:Epithelial Sodium Channel Blockers; D053503:Epithelial Sodium Channels / Q000378:metabolism; D004963:Estrenes / Q000494:pharmacology; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D006868:Hydrolysis; D015640:Ion Channel Gating / Q000187:drug effects*; D007609:Kallidin / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials; D051379:Mice; D008810:Mice, Inbred C57BL; D009318:Natriuresis / Q000187:drug effects*; D009399:Nephrons / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D043783:Receptor, Bradykinin B1 / Q000819:agonists / Q000378:metabolism; D043782:Receptor, Bradykinin B2 / Q000819:agonists / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D012964:Sodium / Q000378:metabolism*; D026941:Sodium Channel Blockers / Q000494:pharmacology*; D019284:Thapsigargin / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D046509:Tissue Culture Techniques; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D062686:Epithelial Sodium Channel Blockers; D053503:Epithelial Sodium Channels; D004963:Estrenes; D019269:Phosphatidylinositol 4,5-Diphosphate; D010726:Phosphodiesterase Inhibitors; D011760:Pyrrolidinones; D043783:Receptor, Bradykinin B1; D043782:Receptor, Bradykinin B2; D026941:Sodium Channel Blockers; D013873:Thionucleotides; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D007609:Kallidin; D002110:Caffeine; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D000450:Aldosterone; D019284:Thapsigargin; C052787:kallidin, des-Arg(10)-; D012964:Sodium; D000242:Cyclic AMP; D010738:Type C Phospholipases; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D001920:Bradykinin