Impaired prostaglandin E1/I2 receptor activity of human blood platelets in acute ischemic heart disease.

The platelets from 74 patients with acute myocardial infarction or with unstable angina showed decreased prostaglandin E1/I2 receptor activity when compared with that of 56 normal volunteers by using [3H]prostaglandin E1 as a probe. In normals, Scatchard analyses showed the presence of one high-affinity-low-capacity (Kd1 = 9.0 +/- 1.2 nM [mean +/- SD]; n1 = 120 +/- 30 sites/cell) and one low-affinity-high-capacity (Kd2 = 1.1 +/- 0.5 microM; n2 = 1,460 +/- 250 sites/cell) prostaglandin E1/I2 receptor population in platelets. In contrast (p less than 0.01), platelets from patients showed decreased ligand binding (n1 = 40 +/- 20 sites/cell; n2 = 800 +/- 210 sites/cell) with little change in the affinity of the receptors (Kd1 = 7.50 +/- 1.6 nM; Kd2 = 0.68 +/- 0.24 microM). On the other hand, the platelets from the patients with dilated cardiomyopathy (n = 7) who were hospitalized for acute chest pain but had normal coronary arteries did not show any impairment of the receptor activity. The plasma prostacyclin...