Plasma Endothelin in Normal and Diabetic Pregnancy

OBJECTIVE To examine endothelin-1 (ET-1) concentrations longitudinally throughout pregnancy in healthy and insulin-dependent diabetic women and to evaluate the relationship between ET-1 and big ET-1 in normal pregnancy. RESEARCH DESIGN AND METHODS Venous blood samples were obtained consecutively in gestational weeks 18, 28, and 38 from 40 healthy women with uneventful pregnancies and 24 pregnant women with IDDM. By radioimmunoassay, plasma ET-1 and big ET-1 were analyzed in the healthy women and plasma ET-1 in the diabetic women. RESULTS In the diabetic pregnant women, plasma ET-1 levels were significantly higher than in healthy pregnant women during the entire observation period (P < 0.001), but did not change with advancing gestational age. Five of the diabetic, but none of the healthy pregnant women, developed preeclampsia. ET-1 levels did not differ between the diabetic women who developed preeclampsia and those who did not. Plasma ET-1 levels in healthy pregnant women were within the range of those in healthy nonpregnant women and did not change during pregnancy. The big ET-1 levels increased and the ET-1/big ET-1 ratio decreased significantly during the observation period. CONCLUSIONS Plasma ET-1 levels do not change with advancing gestational length. During normal pregnancy, the ET-1/big ET-1 ratio decrease, indicating a suppressed converting enzyme activity or altered clearance of ET-1. Pregnant women with IDDM have markedly elevated ET-1 levels. Although diabetic women with and without preeclampsia did not differ with respect to endothelial dysfunction, as reflected by elevated ET-1 concentration, we cannot exclude that altered endothelial function may be of importance for the increased frequency of preeclampsia in pregnant IDDM patients.