Abstract
BackgroundSex steroid hormone receptors have been identified in the adrenal gland of rat, sheep and rhesus monkey, indicating a direct effect of sex steroids on adrenal gland function.MethodsIn the present study, immunohistochemistry using two different mouse monoclonal antibodies was employed to determine the presence of oestrogen receptor alpha (ERalpha) and progesterone receptor (PR) in the mare adrenal gland. Adrenal glands from intact (n = 5) and ovariectomised (OVX) (n = 5) mares, as well as uterine tissue (n = 9), were collected after euthanasia. Three of the OVX mares were treated with a single intramuscular injection of oestradiol benzoate (2.5 mg) 18 – 22 hours prior to euthanasia and tissue collection (OVX+Oe). Uterine tissue was used as a positive control and showed positive staining for both ERalpha and PR.ResultsERalpha staining was detected in the adrenal zona glomerulosa, fasciculata and reticularis of all mare groups. Ovariectomy increased cortical ERalpha staining intensity. In OVX mares and one intact mare, positive ERalpha staining was also detected in adrenal medullary cells. PR staining of weak intensity was present in a low proportion of cells in the zona fasciculata and reticularis of all mare groups. Weak PR staining was also found in a high proportion of adrenal medullary cells. In contrast to staining in the adrenal cortex, which was always located within the cell nuclei, medullary staining for both ERalpha and PR was observed only in the cell cytoplasm.ConclusionThe present results show the presence of ERalpha in the adrenal cortex, indicating oestradiol may have a direct effect on mare adrenal function. However, further studies are needed to confirm the presence of PR as staining in the present study was only weak and/or minor. Also, any possible effect of oestradiol treatment on the levels of steroid receptors cannot be determined by the present study, as treatment time was of a too short duration.
Highlights
Sex steroid hormone receptors have been identified in the adrenal gland of rat, sheep and rhesus monkey, indicating a direct effect of sex steroids on adrenal gland function
Progesterone levels in mare 478 were low (< 3 nmol/l) at the time of euthanasia, but the presence of a cavitated corpus luteum indicated recent ovulation, and the mare was determined to be in metoestrus
The present study demonstrated the presence of both oestrogen receptor alpha (ERα) and progesterone receptor (PR) immunostaining in the cortex of the mare adrenal gland, for PR, only weak staining were observed in a minor proportion of cells
Summary
Sex steroid hormone receptors have been identified in the adrenal gland of rat, sheep and rhesus monkey, indicating a direct effect of sex steroids on adrenal gland function. Activation of the hypothalamic-pituitary-adrenal (HPA) axis, with the release of ACTH and cortisol, as occurs during stress, often has an inhibitory effect on the reproductive system [1,2,3]. Acta Veterinaria Scandinavica 2009, 51:31 http://www.actavetscand.com/content/51/1/31 act in both ways, with reproductive hormones influencing adrenal function. Using a LBA, ERs were found in the adrenal gland of the rat [4]. Using IHC, ERs were found to be localised within cell nuclei of the adrenal cortex of both rhesus monkey [5] and sheep [6]. In the study of Van Lier et al [6], results suggested that both known subtypes of ER, ERα and ERβ, were present in the sheep adrenal gland
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