Long-Term Hypoxia Increases Endothelial Nitric Oxide Synthase Expression in the Ovine Fetal Adrenal

This study was designed to test the hypothesis that fetal adrenal nitric oxide synthase (NOS) is elevated in response to long-term hypoxia (LTH). Pregnant ewes were maintained at high altitude (3820 m) for approximately the last 100 days of gestation. Between days 138 and 141 of gestation, adrenal glands were collected from LTH fetuses and age-matched normoxic controls. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western analysis were used to quantify NOS expression, and NOS distribution was examined by immunohistochemistry and double-staining immunofluorescence for endothelial NOS (eNOS) and 17 alpha-hydroxylase (CYP17). Neuronal NOS (nNOS) was expressed at very low levels and with no differences between groups. Expression of eNOS was significantly greater in the LTH group compared with control. Neuronal NOS was distributed throughout the cortex while the greatest density of eNOS was observed in the zona fasciculata/reticularis area and eNOS co-localized with CYP17. We conclude that LTH enhances eNOS expression in the inner adrenal cortex which may play a role in regulation of cortisol biosynthesis in the LTH fetus.