Plasma thromboxane and prostacyclin: comparison during normal pregnancy and pregnancy complicated by hypertension

Plasma levels of thromboxane B2 (TXB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), 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-PGF1 alpha) for P1 (n = 10) and 142.6 +/- 11.8 (TXB2), 68.5 +/- 5.2 (6-keto-PGF1 alpha) for P2 (n = 10) respectively (pg/ml, mean +/- s.e). In the patients with PIH, TXB2 concentrations increased moderately for P1 (419.2 +/- 21.2; n = 7) and significantly (p less than 0.005) for P2 (452.8 +/- 31.0; n = 7) respectively (pg/ml, mean +/- s.e), while the plasma levels of 6-keto-PGF1 alpha 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-PGF1 alpha was significantly greater (p less than 0.005) in the patients with PIH, where the TXB2/6-keto-PGF1 alpha ratio was 5.2 +/- 0.7 for P1 and 9.4 +/- 2.3 for P2 respectively (mean +/- s.e) compared 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).(ABSTRACT TRUNCATED AT 250 WORDS)