Plasma asymmetric dimethylarginine concentration during the perinatal period

Experimental and clinical evidence has been accumulated to indicate that elevated plasma asymmetric dimethylarginine (ADMA) levels can be regarded as a marker of endothelial dysfunction that mediates cardiovascular morbidity by impairing NO-dependent vascular reactions; therefore, it may have a role in the cardiopulmonary adaptation of the neonate. The present study was undertaken to investigate the perinatal NO metabolism by measuring L-arginine, the NO synthase substrate, ADMA, the endogenous inhibitor of NO synthase, and symmetrical dimethylarginine (SDMA), the biologically inactive L-arginine metabolite in umbilical venous and arterial plasma and in peripheral plasma of the neonate. Measurements were done in ten healthy pregnant women at term delivery and in their newborn infants on the second day of life by using liquid chromatography-mass spectrometry method. It was demonstrated that cord blood L-arginine, ADMA, and SDMA levels were markedly elevated with a moderate, but consistent veno-arterial difference suggesting that they are mainly generated by the placental endothelium. L-Arginine and ADMA levels were found to fall significantly (p < 0.001) by the second postnatal day, whereas SDMA remained unaltered. This finding indicates accelerated enzymatic ADMA elimination and reduction in the inhibition of NO-synthase activity. It is concluded that ADMA may play a role in the control of feto-placental circulation and the circulatory adaptation of the neonate.