INCREASED PLATELET THROMBOXANE-A(2) PROSTAGLANDIN-H(2) RECEPTORS IN PATIENTS WITH PREGNANCY-INDUCED HYPERTENSION

Pregnancy induced hypertension (PIH) is associated with a variety of disturbances in the hemostatic system including alterations in platelet function, thrombocytopenia (1), and an increase in platelet turnover (2,3). The density of platelet Thromboxane A2 (TXA2)/Prostaglandin H-2 (PGH2) receptors was determined in patients with PIH and normal pregnant women, using [I-125]-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+/-60nM, 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.