Thromboxane B-2 in the plasma and amniotic fluid of late pregnant and periparturient sheep.

The concentration of thromboxane (TX) B-2 was similar in plasma from all sources but was significantly greater (P less than 0.01) in amniotic fluid. Fetal hypophysectomy was without effect on maternal or fetal levels of TXB-2 (P greater than 0.1). Neither normal parturition at term nor prematurely induced delivery was associated with any significant trend in TXB-2 levels. During late pregnancy (105--145 days of gestation) the concentrations of TXB-2 and 13, 14-dihydro-15-keto-prostaglandin F (PGFM) in maternal and fetal plasma were significantly correlated (P less than 0.001). There was, however, no correlation between TXB-2 and PGFM levels in samples taken during the 36 h before delivery. These data suggest that thromboxanes play little part in the mechanism of parturition in sheep.