Submitted to: Journal of the Society for Gynecologic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2003
Publication Date: 10/1/2003
Citation: Goodrum, L.A., Saade, G.R., Belfort, M.A., Moise, K.J., Jahoor, F. 2003. Arginine flux and nitric oxide production during human pregnancy and postpartum. Journal of the Society for Gynecologic Investigation. 10(7):401-405. Interpretive Summary: In pregnancy, blood vessels expand to accommodate a larger volume of blood. There seems to be several factors that can cause blood vessels to expand, but the extent to which they are involved in pregnancy is not known. Nitric oxide (NO) is a molecule that is synthesized from the amino acid arginine, and it is known to cause dilation of blood vessels. It is not known, however, whether it is involved in the expansion of blood vessels in pregnancy. In this study we compared second-trimester, third-trimester, and postpartum arginine and nitric oxide production using infusions of the stable isotope L-[15N2]-arginine in normal pregnant women. We found that the rate of production of NO was significantly higher in mid-gestation compared with late gestation and postpartum. Arginine production was significantly higher in early gestation than in late gestation and postpartum. These findings suggest a role for nitric oxide in early cardiovascular adaptation in human pregnancy.
Technical Abstract: To compare second-trimester, third-trimester, and postpartum arginine flux and nitric oxide production using infusions of the stable isotope L-[(15)N(2)]-arginine in normal human gestation, kinetic measurements were made in pregnant volunteers with uncomplicated singleton gestations in mid gestation, late gestation, and more than 8 weeks postpartum. A bolus of 4.95 micromol/kg of labeled arginine was administered, followed by an infusion at 4.95 micromol/kg per hour for 6 hours. The isotopic enrichment of plasma arginine and nitrite or nitrate (NO(x)) was determined by gas chromatography, mass spectrometry, or both. We used the Kolmogorov-Smirnov test for normality, repeated-measures analysis of variance, and Newman-Keuls test. P <.05 denoted statistical significance. The rate of turnover of the intravascular NO(x) pool was significantly higher in mid gestation compared with late gestation and almost reached statistical significance when compared with postpartum values (6.2 +/- 0.9 versus 4.3 +/- 0.8 [P <.02] versus 3.7 +/- 2.1% pool/hour; P =.08). Arginine flux was significantly higher in early compared with late gestation and postpartum (107.8 +/- 13.9 versus 72.5 +/- 16.1 versus 82 +/- 8.8 micromol/kg per hour, respectively; P <.01). Arginine and nitric oxide production is higher in mid gestation. This suggests a role for nitric oxide in early cardiovascular adaptation in human gestations.