title: A comparison of alpha 2-adrenoreceptor binding characteristics of intact human platelets identified by [3H]-yohimbine and [3H]-dihydroergocryptine.
abstract: The binding characteristics of [3H]-yohimbine on intact human platelets were investigated and compared to those of [3H]-dihydroergocryptine. A significant correlation (r = 0.92, P less than 0.01, n = 7) was observed between the inhibition of [3H]-yohimbine binding and of noradrenaline-induced platelet aggregation, indicating that [3H]-yohimbine binds to the alpha 2-adrenoreceptor responsible for noradrenaline-induced platelet aggregation. The binding capacity of [3H]-yohimbine in 20 young male volunteers was 39 +/- 2.2 fmol/10(8) platelets (mean +/- s.e.m.). This is considerably lower than the binding capacity of [3H]-dihydroergocryptine previously reported. Simultaneous analysis of [3H]-yohimbine and [3H]-dihydroergocryptine binding in 10 subjects showed a significantly lower binding capacity for [3H]-yohimbine (P less than 0.001, paired t-test). This difference was not present in every subject, and was consistent within individuals on repeated testing. Possible causes of this difference in radioligand binding are discussed.
mesh_terms: D000328:Adult; D001667:Binding, Competitive; D001792:Blood Platelets / Q000378:metabolism*; D004088:Dihydroergotoxine / Q000097:blood*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D015016:Yohimbine / Q000097:blood*
chemical_list: D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D004088:Dihydroergotoxine; D015016:Yohimbine; D009638:Norepinephrine