Nitric Oxide Inhibits ACTH-Induced Cortisol Production in Near-Term, Long-Term Hypoxic Ovine Fetal Adrenocortical Cells

Abstract

We previously reported that in the sheep fetus, long term hypoxia (LTH) resulted in elevated basal plasma ACTH1–39 while cortisol levels were not different from normoxic controls. We also showed that LTH enhances endothelial nitric oxide synthase (eNOS) expression in the fetal adrenal. This study was designed to determine the effect of nitric oxide on cortisol production in adrenocortical cells from LTH fetal sheep. Ewes were maintained at high altitude (3,820 m) from ~40 days’ gestation (dG) to near term. Between 138–141 dG, fetal adrenal glands were collected from LTH and age-matched normoxic control fetuses. Adrenal cortical cells were pre-treated with sodium nitroprusside (SNP), L-NAME, L-arginine, or Diethyleneamine nitric oxide (DETA-NO) then challenged with 10nM ACTH. Cortisol responses were compared after 1 h. ACTH induced cortisol secretion was significantly higher in LTH vs. control (p<0.01). Enhancement of nitric oxide with L-arginine resulted in a significant reduction of ACTH-mediated cortisol production in the LTH group. DETA-NO also caused a significant decrease in ACTH-mediated cortisol production (p<0.05). Inhibition of NOS with L-NAME significantly increased cortisol production in the LTH group (p<0.05 compared to ACTH alone) while the effect on the control group was not significant. NOS activity was significantly higher in the LTH group compared to control but this difference was eliminated following ACTH treatment. These data indicate that LTH enhances adrenal cortical sensitivity to the inhibitory effects of NO on cortisol production. NO may therefore play an important role in regulating ACTH-induced cortisol production in the LTH fetal adrenal.

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

“…A similar trend was noted in the control but was not significant. L-NAME also counteracted the inhibitory effect of L-arginine on cortisol synthesis (Monau et al 2010). These data clearly illustrate that NO plays a significant role in the regulation of cortisol synthesis in the LTH fetal adrenal.…”

“…In our study, the locus of the ACTH effect on NOS activity in the LTH was not established (Monau et al 2010). However, together with the data showing significant inhibition of cortisol output with NO stimulation and enhanced cortisol output in response to NOS inhibition, it appears that this may be a mechanism(s) of regulating cortisol responses under conditions of LTH.…”

“…None of these effects were observed in normoxic control cells (Monau et al 2010). Fetal adrenal cortical cells display a number of differences from adult adrenocortical cells that may account for the lack of major effects of NO on normoxic fetal adrenal cortical cells in vitro.…”

“…This would exert an inhibitory effect on basal cortisol production overcoming the low level of stimulation by elevated basal ACTH. Stimulation with high levels of ACTH in vitro (Monau et al 2010) or those observed in vivo in response to a secondary stressor (Adachi et al 2004, Imamura et al 2004 would decrease NO activity, thus enhancing cortisol output. We propose that this can occur through ACTH interaction with the MEK/ERK1/2 and/or the AKT/IP 3 .…”

Blockade of nitric oxide synthesis stimulates the activity of adrenal cortex

“…Povećana koncentracija ACTH u grupi tretiranoj sa L-NAME ukazuje na to da je porast u nivou kortikosterona posledica aktivacije HPA osovine. U kulturi adrenokortikalnih ćelija fetusa koji su se razvijali u uslovima hipoksije L-NAME povećava produkciju kortikosterona stimulisanu sa ACTH (22). Suprotno našim rezultatima, pokazano je i da L-NAME ne utiče na bazalne koncentracije ACTH i kortikosterona u pacova (23).…”