PLASMA ENDOTHELIN-1 AND BIG ENDOTHELIN-1 LEVELS IN WOMEN WITH PREECLAMPSIA

To examine a possible role for endothelin-1 (ET-1) and conversion of big ET-1 to ET-1 in the pathophysiology of pre-eclampsia, we measured plasma levels of ET-1 and big ET-1 in 16 women with pre-eclampsia in the third trimester and compared them with those in 11 age-matched normotensive pregnant women and in 10 age-matched pregnant women with chronic hypertension in the third trimester. The plasma concentrations of ET-1 and big ET-1 in the normotensive pregnant women were significantly lower than those in 16 non-pregnant women with a higher molar ratio of big ET-1 to ET-1 in the former group. The plasma concentrations of ET-1 and big ET-1 in the women with pre-eclampsia, on the other hand, were significantly higher than those in the normotensive pregnant women and the molar ratio of big ET-1 to ET-1 in the former group was less than that in the latter group. In sharp contrast, plasma ET-1 and big ET-1 levels in the pregnant women with chronic hypertension were not significantly different from those in the normotensive pregnant women. When examined after delivery, elevated plasma ET-1 and big ET-1 in the women with pre-eclampsia declined, with restoration of normal blood pressure, to the levels in the normotensive women after parturition. There were no significant differences of the levels of ET-1 and big ET-1 in umbilical venous plasma and simultaneously drawn maternal plasma at cesarean section between normotensive pregnant women and women with pre-eclampsia, respectively. These results suggest that normal pregnancy is associated with decreased plasma concentrations of ET-1 with reduced conversion of big ET-1 to ET-1 in maternal vascular endothelial cells, and the derangement of this regulatory system plays an important role in the pathophysiology of pre-eclampsia.