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

Abstract

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 (3,820 m) for approximately the last 100 days of gestation. Between days 138-141 of gestation, adrenal glands were collected from LTH fetuses and age-matched normoxic controls. qRT-PCR and Western analysis were used to quantify NOS expression and NOS distribution was examined by immunohistochemistry and double-staining immunofluorescence for eNOS and 17α hydroxylase (CYP17). 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. nNOS 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.

Comparison of flunixin meglumine and meloxicam influence on postoperative and oxidative stress in ovariohysterectomized bitches

“…Nitric oxide, similarly to prostaglandins, can modulate the release of stress hormones such as CRH, vasopressin, ACTH and corticosterone (Bugajski et al 2004, Rettori et al 2009). NOS activity is increased during stress and infection (Gadek-Michalska et al 2005, Monau et al 2009). Nitric oxide can regulate cortical and medullary adrenal gland functions such as the secretion of aldosterone (Sainz et al 2004) and corticosterone (Cymeryng et al 1998).…”

eNOS activation and NO function: Differential control of steroidogenesis by nitric oxide and its adaptation with hypoxia

“…In that study, however, staining for nNOS was not apparent. We suggested that the differences in nNOS expression between adult and fetus were due to developmental changes (Monau et al 2009). We also demonstrated very low expression levels of iNOS mRNA, but iNOS protein was undetectable with either western analysis or immunohistochemistry.…”

“…eNOS clearly colocalized with CYP17, a key enzyme involved in cortisol synthesis that is expressed in cells of the zona fasciculata (Monau et al 2009). Together, these data further reinforce the concept that adrenal cortical cells express eNOS and that NO produced locally may play a role in local regulation of cortisol synthesis.…”

“…These studies were performed by whole rat adrenals and bovine adrenal cortical and medullary cytosol. Multiple studies later demonstrated immunohistochemical localization of nNOS in the adrenal medulla (Dun et al 1993, Afework et al 1994, Heym et al 1994, Marley et al 1995, Peterson et al 2001, Monau et al 2009.…”

“…A recent study from our laboratory utilized both qRT-PCR and western blot to show that although mRNA for all three NOS isoforms were present in the ovine fetal adrenal cortex, there was no detectable protein expression for iNOS and that eNOS was the predominant isoform (Monau et al 2009). This information was derived from a whole adrenal cortex preparation, however, and did not reveal the actual cellular localization of the eNOS.…”