title: Assessment of binding indices and physiological responsiveness of the 5-HT2 receptor on human platelets.
abstract: This is the first report of parallel studies of binding indices and physiological responsiveness of the "Serotonin-two" (5-HT2) receptor on the human platelet membrane. Binding indices were measured by a microassay employing [125I]ILSD as radioligand and ketanserin to define specific binding. A single receptor population was found, characterized by a KD of 1.69 +/- 0.45 nM and Bmax of 14.5 +/- 6.0 pmol/g protein in healthy subjects. Functional responsiveness of the platelet 5-HT2 receptor complex was assessed by measurement of the extent to which serotonin (10uM) augmented platelet aggregation induced by threshold concentrations of adenosine diphosphate (ADP). A statistically significant positive correlation was found between the number of platelet 5-HT2 receptor sites (Bmax) and the magnitude of the serotonin-amplified aggregation response (r = .70, n = 38, p less than 0.001). Assessment of binding indices and physiological responsiveness of the platelet 5-HT2 receptor complex should facilitate study of age, hormonal, disease, and drug effects on 5-HT2 receptor function in human subjects.
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000328:Adult; D000367:Age Factors; D001792:Blood Platelets / Q000032:analysis*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007650:Ketanserin / Q000494:pharmacology; D008238:Lysergic Acid Diethylamide / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects; D011985:Receptors, Serotonin / Q000032:analysis* / Q000187:drug effects
chemical_list: D011985:Receptors, Serotonin; D000244:Adenosine Diphosphate; D008238:Lysergic Acid Diethylamide; D007650:Ketanserin