Urinary Thromboxane B2 and 11-dehydro-Thromboxane B2 in Normal and Pre-eclamptic Pregnancies

Abstract

The production of urinary thromboxane B2 (TXB2) and 11-dehydro thromboxane B2 (11-dehydro-TXB2), a major urinary metabolite of TXB2, was determined throughout gestation in 25 normotensive pregnant women. These were compared with urinary levels of TXB2 and 11-dehydro-TXB2 in 20 women with mild pre-eclampsia. Urinary TXB2 and 11-dehydro-TXB2 levels did not change with 

gestation. In normal pregnancies urinary levels of TXB2 (geometric mean 0.66 ng/ mg creatinine, 95% CI 0.57 to 0.75) were significantly lower (p<0.0001) than those of 11-dehydro-TXB2 (geometric mean 1.02 ng/mg creatinine, 95% CI 0.92 to 1.13). In women with pre-eclampsia, this was reversed in that urinary levels of TXB2 were higher (geometric mean 1.56, 95% CI 1.22 to 1.99) than those of 11-dehydro TXB2 (geometric mean 0.68, 95% CI 0.52 to 0.87) (p<0.0001). TXB2 levels were higher (p<0.0001) and 11-dehydro-TXB2 levels were lower (p<0.004) in the women with pre-eclampsia than in the controls. This change in metabolism of TXB2 may be the result of an alteration in placental metabolism, since the enzyme responsible for the conversion of TXB2 to 11-dehydro-TXB2 is a placental enzyme. These changes are quite striking, considering that most of the women had mild pre eclampsia, which settled on bed rest. (Thai J Obstet Gynaecol 1990; 2: 11-17.)