IngentaConnect Adrenergic regulation of vascular smooth muscle tone in calf digi...

Authors: C. Belloli¹; P. Badino²; F. Arioli³; R. Odore²; G. Re²

Source: Journal of Veterinary Pharmacology & Therapeutics, Volume 27, Number 4, August 2004 , pp. 247-254(8)

Abstract:

Belloli, C., Badino, P., Arioli, F., Odore, R., Re, G. Adrenergic regulation of vascular smooth muscle tone in calf digital artery. J. vet. Pharmacol. Therap.27, 247–254.

Radioligand binding studies and functional assays on isolated smooth muscle preparations were performed in order to obtain a biochemical and functional characterization of the -adrenoceptor (-AR) subtypes involved in regulation of the smooth muscle relaxation of the calf's common digital artery. The results indicate that the common digital artery possesses two -AR populations (40%₁ and 60%₂) and the ₂-subtype appears to predominate as far as function is concerned. Only the ₂-AR agonists clenbuterol and fenoterol caused dose-related relaxant effects, antagonized by propranolol, when tested in preparations precontracted both with PGF₂ (1.4 × 10^-5 m) and noradrenaline (1.2 × 10^-6 m). In noradrenaline precontracted preparations the ₁-AR selective agonists dobutamine and xamoterol caused vasodilation which was not antagonized by (±)propranolol. While the functional relaxant effects of dobutamine may be attributed to its potent competitive -AR blocking activity, further investigations are required to explain the effect of xamoterol. The vasodilator effect of (±)isoproterenol was irregular. The recorded contractile effects, mainly at dosages greater than 10^-6 m, suggest the loss of drug selectivity for -AR and -AR activation. Indirect evidence indicates that the -adrenoceptor (-AR) population in this tissue which produces a strong contraction is functionally dominant over the -AR, suggesting limited therapeutic benefit for -AR drugs to control blood flow disorders in the calf's distal limb.

Document Type: Research article

DOI: 10.1111/j.1365-2885.2004.00588.x

Affiliations: 1: Department of Animal Health and Welfare, Division of Veterinary Pharmacology and Toxicology, University of Bari, Valenzano, Italy; 2: Department of Animal Pathology, Division of Veterinary Pharmacology and Toxicology, University of Turin, Grugliasco, Turin, Italy; 3: Department of Veterinary Sciences and Technologies for Food Safety, University of Milan, Milan, Italy

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