title: Inhibition of bradykinin-induced increases of cytosolic Ca++ by a novel amiloride analog.
abstract: The present study was undertaken to determine whether activation of the Na+/H+ antiport regulates the bradykinin (BK)-induced Ca++ transient in Madin-Darby canine kidney cells. An amiloride analog, 5-N-N-ethyl[2-methoxy 5-nitrobenzyl]amiloride (L651,548), led to a dose-dependent inhibition of the BK-induced Ca++ transient (Ki = 9 microM), and this effect was eliminated in high external Na+. Zero external Na+ failed to inhibit the BK-induced Ca++ release, suggesting L651,548 is not acting through inhibition of the Na+/H+ antiport. Use of monovalent ionophores to adjust the intracellular pH demonstrated changes in peak Ca++ release by BK only over wide pH ranges. Furthermore, studies revealed L651,548 was much more potent at inhibiting pH recovery (Ki = 55 nM) than BK-induced Ca++ release. Studies in saponin-permeabilized cells demonstrated no effect of L651,548 on inositol trisphosphate-induced Ca++ release. Whole cell [3H] BK binding studies indicated a dose-dependent inhibition by L651,548. We conclude that the Na+/H+ antiport does not play a critical role in control of BK-induced Ca++ release in Madin-Darby canine kidney cells. Also, the amiloride analog L651,548 reduces BK Ca++ release by inhibition of BK receptor binding in Madin-Darby canine kidney cells.
authors.affiliation: Department of Medicine and Pharmacology, Washington University School of Medicine, St. Louis, Missouri.
authors.forename: D W
authors.initials: DW
authors.lastname: Coyne
authors.forename: M
authors.initials: M
authors.lastname: Mordhorst
authors.forename: E J
authors.initials: EJ
authors.lastname: Cragoe
authors.forename: A R
authors.initials: AR
authors.lastname: Morrison
mesh_terms: D000584:Amiloride / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001920:Bradykinin / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D003600:Cytosol / Q000502:physiology; D004285:Dogs; D006863:Hydrogen-Ion Concentration; D008985:Monensin / Q000494:pharmacology; D018002:Receptors, Bradykinin; D017981:Receptors, Neurotransmitter / Q000187:drug effects; D012964:Sodium / Q000494:pharmacology; D017923:Sodium-Hydrogen Exchangers
chemical_list: D002352:Carrier Proteins; D018002:Receptors, Bradykinin; D017981:Receptors, Neurotransmitter; D017923:Sodium-Hydrogen Exchangers; C061007:5-(N-ethyl-(2'-methoxy-5'-nitrobenzyl))amiloride; D000584:Amiloride; D008985:Monensin; D012964:Sodium; D001920:Bradykinin; D002118:Calcium