Interethnic differences in ADMA concentrations and negative association with nitric oxide formation in preeclampsia

Abstract

Recent studies have suggested that impaired nitric oxide (NO) formation in preeclampsia may result from increased concentrations of an endogenous NO synthase inhibitor, the asymmetric dimethylarginine (ADMA). However, no previous study has examined whether a negative association exists between ADMA and nitrite concentrations in preeclampsia. Moreover, no previous study has compared ADMA and nitrite levels in black and white preeclamptic pregnant women. We measured plasma nitrite concentrations using an ozone-based chemiluminescence assay, and plasma ADMA levels using enzyme immunoassays in 94 pregnant (47 healthy pregnant: 16 blacks and 31 whites; and 47 preeclamptic: 14 blacks and 33 whites). We found higher ADMA (2.199 + or -0.016 micromol/l vs. 2.112 + or - 0.012 micromol/l; P<0.0001) and lower plasma nitrite levels (102 + or - 7.1 nmol/l vs. 214.8 + or - 26.1 nmol/l; P<0.0001) in preeclamptic compared with healthy pregnant women. Black pregnant had higher ADMA levels than white pregnant women (P<0.05), both in preeclamptic (2.239 + or - 0.020 micromol/l vs. 2.144 + or - 0.019 micromol/l) and in healthy pregnant (2.172 + or - 0.025 micromol/l vs. 2.077 + or - 0.018 micromol/l). Conversely, we found no significant effects of ethnicity on the plasma nitrite levels, both in healthy pregnant and in preeclamptic women (P>0.05). We found a significant negative correlation (P<0.05) between these markers (r=-0.28; P<0.05). Our findings show higher ADMA and lower nitrite levels in preeclamptic compared with healthy pregnant, and the concentrations of these biomarkers are inversely associated. While ethnicity affected ADMA concentrations, no such effect was found with respect to nitrite levels. These results may have important implications for studies on NO biology and therapeutic approaches of preeclampsia.