title: Alpha 2-adrenoceptors and platelet function in patients with variant angina.
abstract: We have previously reported that platelets of patients with variant angina exhibited pronounced hyperactivity to epinephrine, as assessed by aggregation study. To determine whether this is associated with a change in surface alpha-adrenoceptor status, we investigated the capacity and affinity of binding sites for [3H]dihydroergocryptine, a potent alpha-antagonist, of platelet lysates prepared from 22 patients with ischemic heart disease and 13 control subjects of similar age. [3H]DHE binding capacity to platelets from control subjects, 6 patients with acute myocardial infarction, 9 with effort angina and 7 with variant angina were 233 +/- 44 (SD), 226 +/- 53, 252 +/- 58 and 348 +/- 48 fmol/mg protein and its affinity were 2.05 +/- 1.40, 0.98 +/- 0.46, 1.59 +/- 0.37 and 1.49 +/- 0.66 nM, respectively. The patients with variant angina had significantly higher capacity of platelet alpha-adrenoceptor than controls (49% increase) or patients with other types of ischemic heart disease. In contrast, the affinity for [3H]DHE was not significantly different as compared with other three groups. Similar increments in the binding capacity for [3H]-rauwolscine, alpha 2 antagonist, were found in platelet lysates prepared from 6 patients with variant angina. These results suggest that increased capacity of platelet alpha-adrenoceptor may explain enhanced reactivity to epinephrine in patients with variant angina.
authors.affiliation: First Department of Internal Medicine, Kobe University School of Medicine, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Kusui
authors.forename: M
authors.initials: M
authors.lastname: Yokoyama
authors.forename: H
authors.initials: H
authors.lastname: Fukuzaki
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000378:metabolism* / Q000494:pharmacology; D000328:Adult; D000368:Aged; D000787:Angina Pectoris / Q000097:blood / Q000209:etiology; D000788:Angina Pectoris, Variant / Q000097:blood*; D001792:Blood Platelets / Q000032:analysis* / Q000187:drug effects; D003327:Coronary Disease / Q000097:blood; D003329:Coronary Vasospasm / Q000097:blood; D004088:Dihydroergotoxine / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000097:blood; D005082:Physical Exertion; D010974:Platelet Aggregation / Q000187:drug effects*; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*
chemical_list: D000316:Adrenergic alpha-Agonists; D011942:Receptors, Adrenergic, alpha; D004088:Dihydroergotoxine