Sex steroid modulation of cortisol secretion in sheep

Abstract

There is strong evidence that the gonads modulate the hypothalamic-pituitary-adrenal axis. To investigate these sex differences at the adrenal glands of sheep we compared the cortisol response to ACTH (experiment 1) and measured the relative expression of oestrogen receptor alpha (ERS1), androgen receptor (AR), melanocortin 2 receptor (MC2R) and steroid acute regulatory protein (STAR) mRNA in adrenal glands (experiment 2) of gonadectomised rams and ewes either with or without sex steroid replacement. In experiment 1 six castrated adult rams and four ovariectomised adult ewes were used in two ACTH trials. On each trial blood samples were taken every 15 min for 4 h through an indwelling jugular catheter and each animal received 0.5 mg of an ACTH analogue i.v., immediately after the sample at 1 h from the beginning of the trial. Four days after the first trial the males received 100 mg of Testosterone Cyclopentilpropionate (TC) i.m. and the females received 2.5 mg of Oestradiol Benzoate (EB) i.m. At 72 h after TC or EB administration the second trial was performed. In experiment 2 the adrenal glands were obtained from gonadectomised adult rams (n = 8) and adult ewes (n = 8). Four rams received 100 mg of TC i.m. and four females received 0.5 mg of EB i.m. Blood samples were taken at 0, 12, 24, 48 and 72 h relative to steroid replacement and the animals were thereafter slaughtered. Cortisol, testosterone and 17β-oestradiol were determined by radioimmunoanalysis. The transcripts of ERS1, AR, MC2R and STAR were determined by real-time reverse transcription PCR in adrenal tissue. Cortisol secretion was higher in female sheep than in male sheep, and higher in EB-treated than non-treated ewes. No difference in cortisol secretion was observed between TC-treated and non-treated rams. Gonadectomised rams treated with TC presented greater AR mRNA and MC2R mRNA expression than males without the steroid replacement. Gonadectomised ewes treated with EB tended to present lower AR mRNA than the ones without steroid replacement. Gonadectomised rams with TC also had greater AR mRNA, ERS1 mRNA and MC2R mRNA expression than ewes treated with EB. The relative amount of STAR transcript was not different among the different groups. The results confirm sex differences in ACTH-induced cortisol secretion in sheep, as well as in the expression of the receptor proteins for both 17β-oestradiol and testosterone in the sheep adrenal gland. However, the underlying mechanisms for sex steroid modulation remain unresolved.Keywords: sex steroids, gonadectomy, adrenal, receptors, sheep ImplicationsDifferent stressors result in different responses from the hypothalamus-pituitary-adrenal (HPA) axis and stress can reduce reproductive performance in mammals. Considering the different roles of males and females in reproduction, it is reasonable to think that each sex has its own strategy for dealing with the effects of stress. There is abundant evidence that the gonads affect the way the HPA axis responds to stress. Understanding the regulatory pathways of...

Ejaculation does not contribute to the stress response to electroejaculation in sheep

“…Second, it should also be considered that in general, females have a greater sensitivity to stress than males (Handa, Burgess, Kerr, & O‘Keefe, ; Stefanski & Grüner, ). For example, anestrous or ovariectomized ewes respond to an ACTH challenge secreting more cortisol than rams (Van Lier, Carriquiry, & Meikle, ; Van Lier, Pérez‐Clariget, & Forsberg, ). The lower WBC and ALym amounts observed in ewes than rams may also indicate a greater sensitivity of females than males to stress, as decreases of WBC and Lym are also involved in the stress response in rats (Dhabhar, Malarkey, Neri, & McEwen, ).…”

“…Second, it should also be considered that in general, females have a greater sensitivity to stress than males (Handa, Burgess, Kerr, & O`Keefe, 1994;Stefanski & Grüner, 2006). For example, anestrous or ovariectomized ewes respond to an ACTH challenge secreting more cortisol than rams (Van Lier, Carriquiry, & Meikle, 2014; Van Lier, Pérez-Clariget, & Forsberg, 2003). The lower WBC and ALym F I G U R E 3 (a) Glycaemia and (b) creatine kinase before and after the use of electroejaculation procedures (mean ± SEM) in rams (−♦−) and ewes (-▪-).…”

Plasma ACTH, α-MSH and cortisol variations in the dog during the oestrous cycle in different photoperiods

“…Although several reports on the effect of E 2 on the HPA axis performed in cell cultures and animal models (rats, sheep) are available (McCormick et al 1998;Ochedalski et al 2007;Ogura et al 2008;Kageyama and Suda 2009;Weiser and Handa 2009;Handa and Weiser 2014;van Lier et al 2014), the mechanisms have not yet been fully elucidated. In general, it has been proposed that E 2 could exert a stimulatory effect on the hypothalamus, the corticotroph cells or the adrenal gland cortex (by stimulating CRH secretion or inhibiting glucocorticoid feedback, or stimulating ACTH synthesis or cortisol synthesis/secretion) (Burgess and Handa 1993;Carey et al 1995;McCormick et al 1998;Lo et al 2000;van Lier et al 2003b;Ochedalski et al 2007; Kageyama and Suda 2009;Weiser and Handa 2009;Handa and Weiser 2014;Panagiotakopoulos and Neigh 2014).…”

Aggressive behavior and hair cortisol levels in captive Dorcas gazelles (Gazella dorcas) as animal‐based welfare indicators

“…This difference between groups could be explained due to a gender effect as a consequence of the activity of the sexual hormones. In fact, there is evidence that the gonads modulate the HPA axis, so there are sex differences in the secretion of glucocorticoids [Van Lier et al, ]. It is still unknown which are the basal levels of glucocorticoids in males and females of dorcas gazelles; however, one study assessed hair cortisol concentration in 21 gazelles [Tallo‐Parra et al, ].…”