dihydroergotoxine and Angina-Pectoris--Variant

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.

Topics: Adrenergic alpha-Agonists; Adult; Aged; Angina Pectoris; Angina Pectoris, Variant; Blood Platelets; Coronary Disease; Coronary Vasospasm; Dihydroergotoxine; Female; Humans; Male; Middle Aged; Myocardial Infarction; Physical Exertion; Platelet Aggregation; Receptors, Adrenergic, alpha