ABSENCE OF RELAXATION TO LACTATE IN HUMAN PLACENTAL VESSELS OF PREGNANCIES WITH SEVERE PREECLAMPSIA

OBJECTIVE: Our objective was to determine whether the observed relaxat ion to lactate and other agents in placental vessels of normal pregnan cies is altered in severe preeclampsia. STUDY DESIGN: Isolated placent al arteries and veins from women with severe preeclampsia and uncompli cated term pregnancies were precontracted with prostaglandin F-2 alpha under 5% oxygen and 5% carbon dioxide with the balance nitrogen (Po-2 35 to 38 torr) and then exposed to lactate (1 to 10 mmol/L, pH 7.4, n = 8 to 15), arachidonic acid (0.01 to 10 mu mol/L, n = 6 to 13), nitr oglycerin (1 nmol to 1 mu mol/L, n = 4 to 12), or forskolin (0.01 to 1 0 mu mol/L, n = 6 to 9). The response to lactate was also examined in placental vessels from appropriate-for-gestational-age preterm deliver ies (n = 8) for comparison with a similar group with severe preeclamps ia (n = 8). The t test and analysis of variance statistics were used. RESULTS: Relaxation to lactate was markedly inhibited in both placenta l arteries and veins of women with severe preeclampsia compared with v essels from uncomplicated term or preterm pregnancies. Responses to th e other relaxing agents were not altered in the severely preeclamptic vessels. CONCLUSIONS: In severe preeclampsia absence of lactate-induce d dilatation of placental vessels may contribute to the fetal complica tions associated with impaired blood flow and vasospasm.