Characterization of subtype of alpha1-adrenoceptor mediating vasoconstriction in perfused rat hind limb.
The subtype of alpha1-adrenoceptor mediating the exogenous noradrenaline-induced vasopressor response in perfused rat hind limb was determined by functional measurements and radioligand binding assays. The potencies (pA2 values) of alpha1A-adrenoceptor-selective antagonists, RS-17053 (N-[2-(2-cyclopropylmethoxy-phenoxy) ethyl]-5-chloro-alpha,alpha-dimethyl-1H-indole-3-ethanamine hydrochloride), WB 4101 (2-(2,6-dimethoxyphenoxyethyl) aminomethyl-1,4 benzodioxane), 5-methyl-urapidil, and the alpha1D-adrenoceptor-selective antagonist, BMY 7378 (8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspirol[4.5]de cane-7,9-dione), to inhibit the noradrenaline-induced vasopressor response determined by Schild plot were 9.47 +/- 0.21, 9.48 +/- 0.19, 8.10 +/- 0.27 and 6.66 +/- 0.14, respectively, with no slope significantly different from unity. The affinities (K(i) values) of these antagonists were determined by displacement of 125I-BE 2254 (2-beta(4-hydroxyphenyl)-ethylaminomethyl)-tetralone) binding from the cloned alpha1a-, alpha1b-, alpha1d-adrenoceptor, stably expressed in human embryonic kidney (HEK) 293 cells. The pA2 values of the above antagonists correlated well with the binding K(i) values only for alphaIA-adrenoceptors (r = 0.93), but not for alpha1B-adrenoceptors (r = 0.51) and alpha1D-adrenoceptors (r = 0.13). The concentration-vasopressor response curve for noradrenaline was not significantly affected by pretreatment with 50 microM chloroethylclonidine for 30 min. The results suggest that only alpha1A-adrenoceptors mediate the noradrenaline-induced vasopressor response in perfused rat hind limb.
Zhu
W
W
Institute of Vascular Medicine, The Third Hospital, Beijing Medical University, People's Republic of China.
Zhang
Y
Y
Han
C
C
D058668:Adrenergic alpha-1 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D002460:Cell Line; D003000:Clonidine / Q000031:analogs & derivatives / Q000494:pharmacology; D003001:Cloning, Molecular; D004146:Dioxanes / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005121:Extremities; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010477:Perfusion; D010879:Piperazines / Q000494:pharmacology; D051381:Rats; D018340:Receptors, Adrenergic, alpha-1 / Q000145:classification / Q000502:physiology*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000145:classification; D014661:Vasoconstriction / Q000502:physiology*
D058668:Adrenergic alpha-1 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists; D004146:Dioxanes; D007211:Indoles; D010879:Piperazines; C099495:RS 17053; D018340:Receptors, Adrenergic, alpha-1; D011994:Recombinant Proteins; C051731:chlorethylclonidine; C010654:(2-(2',6'-dimethoxy)phenoxyethylamino)methylbenzo-1,4-dioxane; C053428:BMY 7378; D003000:Clonidine; D009638:Norepinephrine