Effect of the L-Arginine-Nitric Oxide Pathway on Human Placental Vascular Tone and Corticotropin-Releasing Hormone Secretion

Objective: Reduced placental output of nitric oxide (NO) may contribute to increased vascular resistance and abnormally elevated corticotropin-releasing hormone (CRH) levels in umbilical cord plasma in pregnancies complicated by pregnancy-induced hypertension. The aim of this study was to investigate the effects of the NO synthase inhibitor Nω-nitro-L-arginine (L-NOARG) and the NO substrate L-arginine on placental vascular hemodynamics and CRH secretion.Methods: Single lobules of term placentae in vitro, from normal pregnant women were bilaterally perfused with Krebs' solution (5 mL/min, 95% O2, 5% CO2, 37°C, pH 7.3) and changes in fetal arterial pressure (FAP) recorded. Fetal and maternal perfusates were collected at 4°C every 10 min for 3 h and CRH immunoreactivity in perfusates measured by radioimmunoassay.Results: Placentae used in this study, from women aged 28 ± 6 years, had a basal FAP of 23 ± 3 mm Hg (n = 4). Infusion of L-NOARG (100 μM) increased placental FAP (ANOVA, P < 0.05) with no significan...