Increased response to arachidonic acid and U-46619 and resistance to inhibitory prostaglandins in patients with chronic myeloproliferative disorders

In patients with myeloproliferative disorders (MPD) a group of related diseases of the bone marrow stem cell and a recurrent haemorrhagic and/or thrombotic complications, the production of aggregating prostaglandins (PGs) may be normal or slightly reduced, while PGI₂ production is normal. However, MPD platelet sensitivity to antiaggregatory PGs is still unknown. We studied the potency of PGD₂, PGI₂ and PGE₁ as inhibitors of platelet aggregation induced by threshold aggregating concentrations of arachidonic acid and U-46619-analogue of the cyclic endoperoxide PGH₂ in 20 patients with MPD in comparision with healthy controls, with the aim of evaluating the sensitivity of MPD platelets to antiaggregatory PGs. In these patients platelet prostanoid metabolism was normal. However, the functional response of platelets to aggregating and antiaggregating prostanoids was shifted toward potentially increased platelet aggregation response. These findings could have a clinical relevance in view of the haemostatic and thrombotic complications so frequent in MPD.