title: Alpha 2-adrenoceptors in human lymphocytes: direct characterisation by [3H]yohimbine binding.
abstract: [3H]yohimbine, a potent and selective alpha 2-adrenergic antagonist was used to label alpha-adrenoceptors in intact human lymphocytes. Binding of [3H]yohimbine was rapid (t1/2 1.5 -2.0 min) and readily reversed by 10 microM phentolamine (t1/2 = 5 - 6 min) and of high affinity (Kd = 3.7 +/- 0.86 nM). At saturation, the total number of binding sites was 19.9 +/- 5.3 fmol/10(7) lymphocytes. Adrenergic agonists competed for [3H]yohimbine binding sites with an order of potency: clonidine greater than (-) epinephrine greater than (-) norepinephrine greater than (+) epinephrine much greater than (-) isoproterenol; adrenergic antagonists with a potency order of yohimbine greater than phentolamine greater than prazosin. These results indicate the presence of alpha 2-adrenoceptors in human lymphocytes.
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000097:blood; D000317:Adrenergic alpha-Antagonists / Q000097:blood; D001667:Binding, Competitive; D006801:Humans; D007700:Kinetics; D008214:Lymphocytes / Q000378:metabolism*; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D015016:Yohimbine / Q000097:blood*
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine