Serum L-Homoarginine Concentration is Elevated During Normal Pregnancy and is Related to Flow-Mediated Vasodilatation

Background Normal pregnancy is associated with enhanced vasodilatation because of the increased nitric oxide (NO) production. Because L-homoarginine can act as a substrate for NO production, concentrations of L-homoarginine in normal pregnancy were assessed in the present study to test whether L-homoarginine is associated with endothelial function. Methods and Results Healthy non-pregnant (n=61) and pregnant women (n=58) were studied in a cross-sectional study. L-homoarginine, L-arginine, asymmetric dimethylarginine and symmetric dimethylarginine concentrations were determined simultaneously by high-performance liquid chromatography. Endothelium-dependent brachial artery flow-mediated dilation (FMD) was measured by ultrasound. The serum L-homoarginine concentration was significantly higher during the second and the third trimesters compared with the levels in the nonpregnant women (4.8 +/- 1.7 and 5.3 +/- 1.5 vs 2.7 +/- 1.0 mu mol/L, p < 0.001, respectively). In line with this, FMD increased in response to pregnancy (p < 0.05). Three months after delivery, the L-homoarginine concentrations and FMD were comparable to those recorded in the non-pregnant females. The concentration of L-homoarginine correlated significantly with gestational age (r=0.426, p=0.001) and brachial artery diameter and FMD (r=0.362, p=0.006 and r=0.306, p=0.022, respectively) in pregnancy. Conclusions L-homoarginine appears to be increased during the second and third trimesters of pregnancy and may contribute to the enhanced endothelial function in normal pregnancies. (Circ J 2008; 72: 1879-1884)