Increased circulating concentrations of asymmetric dimethyl arginine (ADMA), an endogenous inhibitor of nitric oxide synthesis, in preeclampsia.

OBJECTIVES: To study endogenous nitric oxide (NO) synthesis inhibitors in preeclampsia by measuring asymmetric dimethyl arginine (ADMA) and arginine. STUDY
DESIGN: Blood samples for measurement of plasma concentrations of ADMA and arginine were obtained antepartum (range 32-39 weeks gestation), 3-5 days postpartum and 3 months postpartum from 12 pregnant women with severe preeclampsia and from a normotensive pregnant control group (n=12).
RESULTS: During the third trimester, plasma ADMA was elevated (p<0.05) in the preeclampsia patients (0.55+/-0.02 micromol/l) compared to the normotensive pregnant controls (0.36+/-0.01 micromol/l). Since plasma arginine levels did not differ between preeclamptic and normotensive control women (80.7+/-5.8 micromol/l) and 74.5+/-3.8 micromol/l respectively), the plasma arginine/ADMA ratio was lower (p<0.05) in the preeclamptic group (145.6+/-10.5) compared to the normotensive controls (211.0+/-14.3). Three days post partum there was an increase (p<0.05) in plasma ADMA in both the preeclamptic (0.67+/-0.03 micromol/l) and the normotensive control group (0.64+/-0.03 micromol/l). This was accompanied by a rise (p<0.05) in plasma arginine levels in both the preeclamptic patients (112.9+/-10.5 micromol/l) and the normotensive control group (121.7+/-9.6 micromol/l). At this time point there was no difference in plasma arginine/ADMA ratio between the groups. Three months postpartum, plasma ADMA levels were slightly lower in both groups compared to the postpartum values (preeclampsia: 0.56+/-0.03 micromol/l, normotensive pregnant control: 0.52+/-0.03 micromol/l).
CONCLUSION: Elevated circulating ADMA concentrations in combination with low plasma arginine levels may be of pathophysiological importance in pregnancies complicated with preeclampsia.