Endothelin in primate pregnancy and an experimental preeclampsia-like syndrome

Objectives: To examine the serial changes in circulating endothelin concentration as primate pregnancy advances. To compare peripheral venus and uterine circulations in normal pregnancy and to determine the usefulness of an experimental preeclampsia-like syndrome in examining the placental contribution to total endothelin concentration. Design: Serial measurements of arterial, venous, and uteroplacental endothelin concentration were performed monthly in baboon pregnancy. Endothelin was also measured after reduction in placental blood flow by limited uterine artery ligation and in a sham-operated control. Methods: Ten baboon pregnancies were examined prospectively. Plasma for endothelin concentration was collected from maternal systemic sources and the uteroplacental bed. Endothelin concentration was determined in two operated and a sham-operated controls after reduction of uteroplacental blood flow by angiographically directed selective ligation of a branch of the uterine artery. Signs of a preeclampsia-like syndrome were also examined in these animals. Results: Endothelin concentration progressively decreased as normal pregnancy advanced, with the lowest concentration recorded prior to delivery. After uterine artery ligation, an animal with signs of a severe preeclampsia-like syndrome demonstrated a rise in arterial endothelin concentration at the time of delivery. This did not appear to arise from the uteroplacental circulation. Conclusions: Elevated endothelin concentrations in human preeclampsia, a late pregnancy event, should be interpreted in light of decreased concentrations at this time in normal primate pregnancy. Endothelin may be a marker of disease severity in human preeclampsia.