Reactivities to serotonin and histamine in umbilical and placental vessels during the third trimester after normotensive pregnancies and pregnancies complicated by preeclampsia.

OBJECTIVE

The aim of the study was to evaluate responses of umbilical and placental arteries and veins to serotonin and histamine after normotensive pregnancies and pregnancies complicated by preeclampsia.

STUDY DESIGN

Each pair of placentas from a normotensive woman and a woman with preeclampsia was matched for gestational age. Rings of these vessels were prepared and mounted in tissue baths under their respective optimal passive tension. Cumulative concentration-response curves to serotonin and histamine were measured.

RESULTS

Responses to serotonin were decreased in umbilical vessels from the preeclampsia group with respect to the normotensive group. This is reflected by reduced maximum responses and sensitivity (negative logarithm of the 50% effective concentration) to serotonin. Maximum response to serotonin was significantly decreased in placental vein rings from the preeclampsia group. We recorded a decreased maximal response to histamine in placental vein rings from pregnancies complicated by preeclampsia with respect to those from normal pregnancies. Among normotensive women there was a significant positive linear relationship between neonatal weight and sensitivity to serotonin in umbilical and placental veins. This relationship was totally absent in preeclampsia. Sensitivity to histamine was linearly related to neonatal weight in umbilical vessels of the pooled results of both experimental groups.

CONCLUSION

The vasoconstrictive effects of serotonin, but not those of histamine, are decreased in umbilical and placental vessels after preeclampsia. Sensitivities to serotonin and histamine change in umbilicoplacental vessels during the third trimester. Altered reactivity to serotonin may play a significant role in the reduction of umbilicoplacental blood flow in preeclampsia.