Prostacyclin and platelet aggregation in sickle cell disease

Patients with sickle cell disease have been described to have decreased platelet aggregation. The cause of this decrease is believed to be the refractory state of platelets from continual in vivo activation. In this study, plasma 6-keto PGF1 alpha (stable metabolite of vessel wall-derived prostaglandin, prostacyclin) levels were measured to study the mechanism of decreased platelet aggregation. Plasma 6-keto PGF1 alpha levels were measured by radioimmunoassay in ten patients with sickle cell disease and in ten control subjects. Plasma 6-keto PGF1 alpha levels in normal subjects ranged from 0 to 100 pg/ml (mean 40 +/- 14 pg/ml), but were significantly higher in patients with sickle cell disease (range 170 to 880 ng/ml, mean 446 +/- 89 pg/ml, P less than .002). Platelet aggregation in response to an endoperoxide analog in these patients was lower compared with that of the control subjects. This study suggests that prostacyclin activity is increased in subjects with sickle cell disease. This increased activity is probably due to persistent stress to the endothelium from hemolysis and continual platelet activation. Decreased platelet aggregation seen in these patients may be due to elevated prostacyclin activity.