Expression and Distribution of Glucocorticoid Receptors in the Ovine Fetal Adrenal Cortex: Effect of Long-term Hypoxia

Abstract

This study was designed to determine if long-term hypoxia (LTH) alters adrenal glucocorticoid receptor (GR) expression in the ovine fetal adrenal cortex. Ewes were maintained at 3820 m from approximately 30 to 138 to 140 days' gestation, and fetal adrenals were collected. Western analysis revealed two approximately 94-kDa GR-alpha isoforms and a lower molecular weight (45 kDa) form. A decreasing trend in the ratio of 94-kDa/45-kDa bands following LTH suggested an increase in GR turnover. Immunohistochemistry demonstrated dense GR staining in the zona glomerulosa with minimal staining in the zona fasciculata in the control group, while dense staining was observed throughout the cortex in LTH. Western analysis and reverse transcription polymerase chain reaction confirmed that the GR- beta isoform is not present or expressed at extremely low levels in the fetal adrenal, hypothalamus, pituitary, and placenta. These data indicate that LTH alters GR-alpha function in the fetal adrenal cortex and suggest that GR-beta is not expressed in sheep.

Maternal Undernutrition Programs Offspring Adrenal Expression of Steroidogenic Enzymes

“…9,12 Adrenal ACTH receptor (ACTH-R) 14,15 mediates a long-loop feedback axis, by which the hypothalamus/pituitary regulate the expression of steroidogenic enzymes.…”

“…Glucocorticoids play an essential role in the stress response and have been proposed to alter signal transduction in the adrenal cortex thereby regulating adrenocorticotropic hormone (ACTH) sensitivity. [9][10][11] In addition to negative feedback regulation at the hypothalamic-pituitary level, glucocorticoid feedback may occur at the adrenal level, 12,13 mediated by adrenal glucocorticoid receptor (GCR)/mineralocorticoid receptor (MCR). 9,12 Adrenal ACTH receptor (ACTH-R) 14,15 mediates a long-loop feedback axis, by which the hypothalamus/pituitary regulate the expression of steroidogenic enzymes.…”

Effects of Maternal Dexamethasone Treatment Early in Pregnancy on Glucocorticoid Receptors in the Ovine Placenta

“…It was suggested that the expression of GRb is either very low in sheep placenta or the previously reported GRb antibody, whose specificity can now be tested with a blocking peptide, revealed a non-specific binding of GRb. 37 In a very recent study, Saif et al identified 12 isoforms of the GR in the human placenta, which were localized to the trophoblast cells and expression varied in relation to cellular location in either the cytoplasm or nucleus, fetal sex, fetal size, but not all isoforms were expressed in every individual. 40 Therefore, we would like to suggest that other GR isoforms may also be present in the sheep placenta, which could contribute to the changes observed in GRt protein but not GRa protein, but this has to be elucidated in the future.…”

“…31 The specificity for GRt and GRα has been previously demonstrated 30,36 and was confirmed in this study with Western blotting (Figure S1). Briefly, incubation with monoclonal mouse antirat GRt at 1:50 (MA1-510, Thermo Scientific, Utah), 36 polyclonal rabbit antihuman GRα at 1:100 (P-20:sc1002, Santa Cruz), 30 or polyclonal rabbit antihuman GRβ at 1:100 (PA3-514, Thermo Scientific) 30,37 diluted in 2% normal goat serum was performed in a humidity chamber at 4°C overnight. Tissue sections were incubated with biotinylated antirabbit immunoglobulin G (IgG) antibody (PK-4001 Vectastain ABC kit, Vector Laboratories) at 1:200 and treated with ABC solution for 60 minutes (PK-4001 Vectastain ABC kit, Vector Laboratories California).…”

Review: The role of multiple placental glucocorticoid receptor isoforms in adapting to the maternal environment and regulating fetal growth

“…Early studies in sheep demonstrated multiple GR isoforms in the adult adrenal gland [62] and indeed studies have demonstrated the presence of at least three GR isoforms in the sheep placenta [63]. Given that the human, monkey, mouse and rat all have the second start codon on exon 2 that the guinea pig is missing, it is likely that the monkey, mouse and rat would have a GR expression profile similar to that of human.…”