Vasoactive mediators in pregnancy-induced hypertensive disorders: a longitudinal study

Abstract

Objective: The objective of this study was to evaluate the extent to which endothelin and the eicosanoids prostacyclin and thromboxane A2 are involved in the pathophysiology of gestational hypertension and preeclampsia.

Study design: In a longitudinal design, venous blood samples and 24-hour urine specimens were collected from 396 women in each trimester of pregnancy. After delivery of all patients, venous plasma endothelin was assessed in 20 subjects with identified preeclampsia, 48 subjects with gestational hypertension, and 59 normotensive subjects. Urinary excretions of the thromboxane A2 and of the prostacyclin metabolites thromboxane B2 and 6-keto-prostaglandin F1 alpha were assessed in 16 subjects with preeclampsia, 35 subjects with gestational hypertension, and 31 normotensive subjects.

Results: Endothelin levels showed a second-trimester drop in all groups. In all 3 gestational trimesters a high correlation was found between the excretion of thromboxane B2 and that of 6-keto-prostaglandin F1 alpha (P <.001). The overall thromboxane B2 and 6-keto-prostaglandin F1 alpha urinary excretions increased throughout pregnancy and the overall thromboxane B2 /6-keto-prostaglandin F1 alpha ratio decreased. No significant differences in endothelin, thromboxane B2, and 6-keto-prostaglandin F1 alpha excretion levels or in thromboxane B2 /6-keto-prostaglandin F1 alpha ratios were found between women with preeclampsia, gestational hypertension, and normotension. Only in a small group of patients with severe preeclampsia (n = 2) and severe gestational hypertension (n = 2) were increased second-trimester endothelin values and increased thromboxane B2 /6-keto-prostaglandin F1 alpha ratios found.

Conclusion: In this longitudinal study we found no evidence for prostacyclin deficiency or increased endothelin levels in preeclampsia. Only women with severe preeclampsia and severe gestational hypertension expressed increased endothelin levels and thromboxane dominance over prostacyclin.