title: Effects of impromidine- and arpromidine-derived guanidines on recombinant human and guinea pig histamine H1 and H2 receptors.
abstract: Imidazolylpropylguanidines derived from impromidine and arpromidine are more potent and efficacious agonists at the guinea pig histamine H2 receptor (gpH2R) than at the human H2R (hH2R) in the GTPase assay. Additionally, such guanidines are histamine H1 receptor (H1R) antagonists with preference for the human relative to the guinea pig receptor. The purpose of this study was to examine structure-activity relationships of guanidines at human and guinea pig H1R and H2R species isoforms expressed in Sf9 insect cells. Three impromidine analogues and six arpromidine analogues exhibited agonistic activity at H2R and antagonistic activity at H1R as assessed in the steady-state GTPase assay. Species selectivity of derivatives was similar as compared with the parent compounds. None of the structural modifications examined (different aromatic ring systems and different ring substituents) was superior in terms of H2R potency and efficacy relative to impromidine and arpromidine, respectively. These data point to substantial structural constraints at the agonist binding site of H2R. Guanidines exhibited distinct structure-activity relationships for H1R antagonism in a radioligand competition binding assay and the GTPase assay and for H1R inverse agonism. Our data indicate that it is difficult to obtain guanidine-type agonists with high potency and high efficacy for hH2R, but those compounds may be useful tools for exploring the antagonist binding site and constitutive activity of H1R.
authors.affiliation: High Throughput Screening Laboratory, University of Kansas, Lawrence, USA.
authors.forename: Sheng-Xue
authors.initials: SX
authors.lastname: Xie
authors.forename: Fabian
authors.initials: F
authors.lastname: Schalkhausser
authors.forename: Qi-Zhuang
authors.initials: QZ
authors.lastname: Ye
authors.forename: Roland
authors.initials: R
authors.lastname: Seifert
authors.forename: Armin
authors.initials: A
authors.lastname: Buschauer
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D002460:Cell Line; D020558:GTP Phosphohydrolases / Q000378:metabolism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000187:drug effects / Q000235:genetics; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000187:drug effects / Q000235:genetics; D006146:Guanidines / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D006168:Guinea Pigs; D017442:Histamine Agonists / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D006634:Histamine H1 Antagonists / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D007093:Imidazoles / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D017446:Impromidine / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D007313:Insecta; D015394:Molecular Structure; D011738:Pyrilamine / Q000378:metabolism; D011969:Receptors, Histamine H1 / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D011970:Receptors, Histamine H2 / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000187:drug effects; D013329:Structure-Activity Relationship; D014162:Transfection
chemical_list: D006146:Guanidines; D017442:Histamine Agonists; D006634:Histamine H1 Antagonists; D007093:Imidazoles; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D011993:Recombinant Fusion Proteins; C060591:arpromidine; D017446:Impromidine; D020558:GTP Phosphohydrolases; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D019205:GTP-Binding Protein alpha Subunits, Gs; D011738:Pyrilamine