title: Beta-adrenoceptors in equine trachea and heart.
abstract: The density and subtype pattern of beta-adrenoceptors in equine tracheal epithelium, tracheal smooth muscle and heart from 6-9 horses were investigated by radioligand binding studies using the nonselective beta-adrenoceptor antagonist 125I-cyanopindolol (ICYP). The specific binding of ICYP was 341 +/- 162 fmol/mg protein (mean +/- SD) for epithelium, 42 +/- 13 fmol/mg for smooth muscle and 124 +/- 39 and 101+/- 19 fmol/mg for the cardiac atrium and ventricle, respectively. The Kd value of ICYP was 6.7 10.2 pmol/L. In competition studies, different concentrations of either the beta2-selective drug ICI 118551 or the beta1-selective CGP 20712A competed with 25 pmol/L ICYP for the binding sites. The competition curves for tracheal smooth muscle and epithelium were monophasic with an approximate Kd value for ICI 118551 of 1 nmol/L and for CGP 20712A of 10000 nmol/L. This corresponds to known Kd values for these substances binding to beta2-adrenoceptors. beta2-Adrenoceptors were also found in the heart, most pronounced in the atrium, where the density was 29% +/- 6% (mean +/- SD) of the total receptor density. CGP 20712A and ICI 118551 bound to the dominating binding site of beta1-adrenoceptors in the heart with Kd values of approximately I nmol/L and 100 nmol/L, respectively.
authors.affiliation: Swedish University of Agricultural Sciences, Faculty of Veterinary Medicine, Department of Pharmnacology and Toxicology, Uppsala.
authors.forename: K
authors.initials: K
authors.lastname: Töneke
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D005260:Female; D006325:Heart Atria / Q000378:metabolism; D006352:Heart Ventricles / Q000378:metabolism; D006736:Horses / Q000378:metabolism*; D007093:Imidazoles / Q000378:metabolism; D007457:Iodine Radioisotopes; D008024:Ligands; D008297:Male; D009130:Muscle, Smooth / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D011412:Propanolamines / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D012044:Regression Analysis; D013051:Spectrometry, Gamma / Q000662:veterinary; D014132:Trachea / Q000378:metabolism*
chemical_list: D000319:Adrenergic beta-Antagonists; D007093:Imidazoles; D007457:Iodine Radioisotopes; D008024:Ligands; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; C026777:ICI 118551; C047975:cyanopindolol; D010869:Pindolol; C049763:CGP 20712A