Identification of beta-adrenoceptors in bovine teat muscles by 3H-dihydroalprenolol binding.
beta-Adrenoceptors present in smooth muscles of the cistern wall of teats of lactating cows were identified and characterized by 3H-dihydroalprenolol (DHA) binding. Binding association and dissociation at 37 degrees C were very rapid (t1/2 amounting to 2 min and 1 min 30 sec respectively), stereospecific and saturable. By Scatchard analysis, the mean receptor density was 92 fmol of 3H-dihydroalprenolol bound/mg protein and the dissociation constant was 0.63 nM. The Hill number was 1.01. The order of potency of catecholamines for the binding was (-)-isoproterenol greater than (-)-epinephrine greater than (-)-norepinephrine, indicating a population of mainly beta 2-adrenoceptors. Potency series of 10 antagonists and 15 agonists, determined from binding-inhibition experiments, were composed.
D000526:Alprenolol / Q000031:analogs & derivatives*; D000818:Animals; D002417:Cattle; D004082:Dihydroalprenolol / Q000378:metabolism*; D005260:Female; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D008321:Mammary Glands, Animal / Q000378:metabolism*; D009130:Muscle, Smooth / Q000378:metabolism*; D011869:Radioligand Assay; D011943:Receptors, Adrenergic, beta / Q000032:analysis*; D014316:Tritium; D014325:Tromethamine
D011943:Receptors, Adrenergic, beta; D014325:Tromethamine; D014316:Tritium; D004082:Dihydroalprenolol; D000526:Alprenolol