Abstract

Pregnancy induced hypertension (PIH) is associated with a variety of disturbances in the hemostatic system including alterations in platelet function, thrombocytopenia, and an increase in platelet turnover. The density of platelet Thromboxane A2 (TXA2)/Prostaglandin H2 (PGH2) receptors was determined in patients with PIH and normal pregnant women, using [125I]-PTA-OH, a TXA2/PGH2 receptor antagonist. The number of platelet TXA2/PGH2 receptors significantly increased (p < 0.008) from 1734 +/- 370 sites/platelet (n = 8) in normal pregnant women to 3703 +/- 846 sites/platelet (n = 9) in patients with severe PIH. The sensitivity of platelets to the TXA2 mimetic U46619 was significantly (p < 0.0005) increased in platelets obtained from severe PIH patients (EC50 = 150 +/- 10nM, n = 3) compared to controls (EC50 = 290 +/- 60 nM, n = 5). These results indicate that an increased number of TXA2/PGH2 receptors as well as increased sensitivity to TXA2/PGH2 mimetics occurs in PIH. Collectively, these results provide further support for the notion that TXA2 and its receptor may play an important role in the pathophysiology of PIH.