Administration of the
nitric oxide synthase (NOS) inhibitor,
NG-nitro-L-arginine methyl ester (
L-NAME) during pregnancy has been shown to compromise fetal growth. This study was designed to determine whether
aminoguanidine, a predominate inhibitor of inducible NOS, affects fetal outcome. In addition, we extended the prenatal administration of
L-NAME into the postnatal period (14 d) to determine whether neonatal growth and maturation were also affected.
L-NAME, but not
aminoguanidine, compromises fetal and placental growth. When compared with control 14-d-old pups, postnatal
L-NAME compromised neonatal growth, whether it was given directly (intraperitoneally) (39.7 +/- 1.1 versus 24.1 +/- 1.0 g) or indirectly (38.6 +/- 0.5 versus 22.2 +/- 1.2 g) via maternal breast milk. Neonatal growth retardation was asymmetric, with brain sparing, suggesting a nutritional origin.
L-NAME administration resulted in growth retardation that extended into adulthood, without evidence of catch-up growth. Treated neonates displayed the hallmarks of
hypertrophic pyloric stenosis. Significant increases in stomach weight/pup weight (9.9 +/- 0.3 versus 8.2 +/- 0.4 x 10(3)) and stomach volume/pup weight (12.0 +/- 0.6 versus 9.4 +/- 0.6 mL/100 g) with a concomitant decrease in small intestine weight/length (2.10 +/- 0.08 versus 3.18 +/- 0.13 g/100 cm) was noted in treated versus control pups (p < 0.05). Muscularis
hypertrophy at the pyloric sphincter in the
L-NAME-treated pups was noted by histology. Blood pressure was elevated in the
L-NAME-treated pups (93 +/- 6 versus 60 +/- 5 mm Hg in control pups, p < 0.05). These findings are consistent with inhibition of neuronal and endothelial NOS activity. We conclude that NO, formed via the constitutive
isoforms of NOS, is a critical determinant of fetal and neonatal growth and maturation.