title: L-163,491 is a partial angiotensin AT(1) receptor agonist in the hindquarters vascular bed of the cat.
abstract: Responses to the nonpeptide angiotensin II agonist 5, 7-Dimethyl-2-ethyl-3-[[2'-([butyloxycarbonyl) aminosulfonyl]-5'-(3-methyoxybenzyl)-[1, 1'-biphenyl]-4-yl]methyl]-3H-imidazo[4,5-b]pyridine (L-163,491) were investigated and compared with responses to angiotensin II, angiotensin IV and norepinephrine in the hindquarters vascular bed of the cat under constant-flow conditions. Injections of L-163,491 into the hindquarter perfusion circuit caused dose-related increases in hindquarters perfusion pressure. In relative terms, angiotensin II was more potent than norepinephrine, which was more potent than angiotensin IV and L-163,491 in increasing hindlimb vascular resistance. The slope of the dose-response curve for L-163,491 was flat, while the apparent affinity of the compound for angiotensin AT(1) receptors was slightly greater than angiotensin IV. Responses to L-163,491 were inhibited by the angiotensin AT(1) receptor antagonist DuP 532 (2-propyl-4-pentafluoroethyl-1-[2'-(1H-tetrazol-5-yl)bipheny l-4-yl)me thyl]imidazole-5-carboxylic acid) and were not altered by the angiotensin AT(2) receptor antagonist PD123,319 (S(+)-1-[[4-(Dimethylamino)-3-methylphenyl]methyl]-5-(diphenylacetyl+ ++) -4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid ditribluoroacetate). However, the increase in hindlimb perfusion pressure in response to angiotensin II and angiotensin IV was significantly decreased following injection of L-163,491. These data suggest that the nonpeptide angiotensin analog L-163,491 has partial agonist activity, which is dependent on the stimulation of angiotensin AT(1) receptors in the hindquarters vascular bed of the cat.
authors.affiliation: Department of Pharmacology SL83, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70112, USA.
authors.forename: B J
authors.initials: BJ
authors.lastname: De Witt
authors.forename: E A
authors.initials: EA
authors.lastname: Garrison
authors.forename: H C
authors.initials: HC
authors.lastname: Champion
authors.forename: P J
authors.initials: PJ
authors.lastname: Kadowitz
mesh_terms: D000804:Angiotensin II / Q000031:analogs & derivatives* / Q000502:physiology; D000818:Animals; D002415:Cats; D004305:Dose-Response Relationship, Drug; D005260:Female; D006614:Hindlimb / Q000098:blood supply; D007093:Imidazoles / Q000494:pharmacology*; D008297:Male; D011725:Pyridines / Q000494:pharmacology*; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000819:agonists* / Q000378:metabolism; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
chemical_list: D007093:Imidazoles; C096715:L 163491; D011725:Pyridines; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; C012877:angiotensin II, des-Asp(1)-des-Arg(2)-Ile(5)-