Abstract
Plasma levels of thromboxane B2 (TXB2) and 6-keto-prostaglandin F1a (6-keto-PGF la), stable metabolites of two prostanoids with opposing biological effects, TXA2 and prostacyclin, were measured by radioimmunoassay in normal pregnancy (controls) and pregnancy complicated by hypertension (PIH) from 32 to 36 (Period 1; P1) and from 36 to 40 (Period 2; P2) weeks of gestation. The plasma concentration of each compound in the control subjects was 265.6±58.4 (TXB2), 132.4±16.5 (6-keto-PGF 1α) for P1 (n=10) and 142.6±11.8 (TXB2), 68.5±5.2 (6-keto-PGF1α) for P2 (n=10) respectively (pg/ml, mean±s.e). In the patients with PIH, TXB2 concentrations illcreased moderately for P1 (419.2±21.2;n=7) and significantly (P<0.005) for P2 (452.8±31.0; n=7) respectively (P9/ml, mean±s.e), while the plasma levels of 6-keto-PGF1α revealed a slight to moderate decrease both for P1 (84.5±4.0; n=7) and P2 (59.7±8.1; n-7) respectively (pg/ml, mean±s. e). The physiological balance of TXB2 to 6-keto-PGF1α was significantly greater (P<0.005) in the patients with PIH, where the TXB2/6-keto-PGF1α ratio was 5.2±0.7 for PI and 9.4±2.3for P2 res ectivel mean±s.e com ared with that of the controls, where it was 2.4±0.4 for P1 and 2.0±0.2 for P2 respectively (mean±s. e). Thus, in the patients with PIH, vasoconstricting and proaggregating prostanoid showed a dramatic rise in the maternal circulation, suggesting the possibility that platelet activation would play an important role in eliciting clinical pictures associated with PIH.
