title: Novel amiloride analog allosterically modulates the alpha 2-adrenergic receptor but does not inhibit Na+/H+ exchange.
abstract: Two novel amiloride analogs have been synthesized during the course of efforts to develop a photoaffinity label for the amiloride allosteric domain on alpha 2-adrenergic receptors. One of these, 5-[N-2'-aminoethyl-N'-isopropyl]amiloride-N-[4"-azidosalicylamide] (A-EIA-AS), markedly accelerates the rate of dissociation of [3H]yohimbine from affinity-purified alpha 2-adrenergic receptors, an assay for allosteric modulation of receptor-adrenergic ligand interactions. In contrast, this agent does not appreciably inhibit Na+/H+ exchange, measured as 5-(N-ethyl-N-isopropyl)amiloride (EIA)-inhibitable 22Na+ uptake into cultured renal epithelial cells. A second analog, 5-[N-2'-(4"-azidosalicylamidino)ethyl-N'- isopropyl]amiloride (ASA-EIA), does not foster an accelerated rate of dissociation of [3H]yohimbine binding from the alpha 2 receptor but does block the ability of A-EIA-AS to do so, suggesting that ASA-EIA and A-EIA-AS interact at a common binding site. Interestingly, the ability of EIA to accelerate [3H]yohimbine dissociation is not blocked by ASA-EIA, a finding that may indicate that EIA and A-EIA-AS allosterically modulate alpha 2 receptor-ligand interactions via distinct or nonoverlapping binding sites.
authors.affiliation: Department of Pharmacology, Vanderbilt University, School of Medicine, Nashville, Tennessee 37232-6600.
authors.forename: A L
authors.initials: AL
authors.lastname: Wilson
authors.forename: S W
authors.initials: SW
authors.lastname: Womble
authors.forename: C
authors.initials: C
authors.lastname: Prakash
authors.forename: E J
authors.initials: EJ
authors.lastname: Cragoe
authors.forename: I A
authors.initials: IA
authors.lastname: Blair
authors.forename: L E
authors.initials: LE
authors.lastname: Limbird
mesh_terms: D000584:Amiloride / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors*; D002478:Cells, Cultured; D007668:Kidney / Q000187:drug effects / Q000378:metabolism; D011487:Protein Conformation; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects* / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers; D013552:Swine; D014316:Tritium; D015016:Yohimbine / Q000378:metabolism
chemical_list: D000889:Anti-Arrhythmia Agents; D002352:Carrier Proteins; D011942:Receptors, Adrenergic, alpha; D017923:Sodium-Hydrogen Exchangers; D014316:Tritium; C076305:5-(N-2'-(4''-azidosalicylamidino)ethyl-N'-isopropyl)amiloride; C076306:5-(N-2'-aminoethyl-N'-isopropyl)amiloride-N-(4''-azidosalicylamide); D015016:Yohimbine; D000584:Amiloride; C039614:ethylisopropylamiloride