Affinity of isoxsuprine for adrenoreceptors in equine digital artery and implications for vasodilatory action
Articolo
Data di Pubblicazione:
2000
Citazione:
Affinity of isoxsuprine for adrenoreceptors in equine digital artery and implications for vasodilatory action / C. Belloli, R. Carcano, F. Arioli, C. Beretta. - In: EQUINE VETERINARY JOURNAL. - ISSN 0425-1644. - 32:2(2000 Mar), pp. 119-124.
Abstract:
We used isolated equine digital arteries to study the vasodilatory mechanism of isoxsuprine, and fowl caecum preparations to investigate the affinity of the drug for β-adrenoceptors. Isoxsuprine is a potent vasodilator of arterial smooth muscle that has been precontracted by an α-adrenoceptor agonist such as noradrenaline (log EC50 = -6.33 [-5.98; -6.68]). The present study indicates that its effect is due to α-adrenoceptor blockade since: (1) after a long lasting exposure to cumulative doses of isoxsuprine the vasoconstricting action of noradrenaline cannot be restored; (2) isoxsuprine does not promote relaxation on preparations precontracted by PGF2α; (3) isoxsuprine shifts the dose-response curve of noradrenaline to the right; and (4) its affinity (pKB = 6.90 [6.60; 7.20]) in this experiment is comparable to that in noradrenaline-precontracted preparations and is 14 times lower than that of the selective α1-adrenergic antagonist prazosin [pKB = 8.04 (7.40; 8.68]). The affinity of isoxsuprine for β-adrenoceptors was 100 times lower than that of isoprenaline when tested on fowl caecum. This preparation has a large β-adrenoceptor and negligible α-adrenoceptor population concerned with the control of smooth muscle motility. Our data suggest that the α-mediated effect of isoxsuprine on horse arterial smooth muscle is due to higher affinity of the drug for α- than β-adrenoceptors rather than low concentration or functionality of β-sites at this site. According to these data, pure β2-agonists seem to be more profitable tools to determine vasodialtion of the arterial bed in horses legs.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
β-adrenoceptors; Equine digital artery; Fowl caecum; Horse; Isoxsuprine
Elenco autori:
C. Belloli, R. Carcano, F. Arioli, C. Beretta
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