Expression of arginine vasotocin and estrogen receptor alpha (ERα) in the shell gland altered by the specific phase relations of neural oscillations affects the reproductive physiology of Japanese quail

Expression of estrogen receptor alpha in response to stress and estrogen antagonist tamoxifen in the shell gland of Gallus gallus domesticus: involvement of anti-oxidant system and estrogen

Animals are frequently exposed to various kinds of environmental stressors and estrogen is known to play important role in stress response besides its crucial role in regulation of cellular proliferation, metabolic activity and reproduction. The study investigates the estrogen antagonist, tamoxifen (TM), mediated estrogen receptor alpha (ERα) expression, to modulate stress induced parameters in chickens. The study further explores the activity of superoxide dismutase (SOD), catalase and glutathione peroxidase (GPX) and malonaldehyde (MDA) in brain, ovary and shell gland during water deprivation (WD) and tamoxifen administration in sexually mature chicken. WD and TM administration both decrease the plasma estradiol while WD increases corticosterone. WD also elevates MDA concentration in the brain, ovary and shell gland while TM lowers it. WD and TM administration lowers the specific activity of SOD in brain and shell gland. In contrast, WD increases the specific activity of catalase, GPx and GR in the brain and shell gland, while TM decreases it. It appears that endogenous estradiol plays a crucial role in expression of antioxidant enzymes and tamoxifen acts as an antioxidant by reducing the oxidative stress in chicken. Abundant expression of ERα has been observed in the shell gland of egg laying birds while stress like water deprivation and TM down-regulates its expression. Thus, it can be concluded that expression of ERα in shell gland plays a predominant role in mediating estrogen action in response to water deprivation stress and tamoxifen.

Water and Food restriction decreases immunoreactivity of oestrogen receptor alpha and antioxidant activity in testes of sexually mature Coturnix coturnix japonica

Food and water are closely associated with reproductive willingness in vertebrates. These are important for animals and their non-availability act as stressors which decrease sex steroid secretion suppressing reproductive behaviour. Oestrogen plays a crucial role in reproduction via its receptors alpha (ERα) and beta (ERβ). This study tested the hypothesis that ERα in testes of male Japanese quail is regulated during water and food deprivations. The present study reveals that both water and food deprivations cause oxidative stress and subsequently decrease catalase and superoxide dismutase activity, while these increase malondialdehyde and hydrogen peroxide. Both deprivations reduce plasma oestradiol whereas elevate corticosterone level. The immunofluorescent localization of ERα in the testes occurs predominantly in the seminiferous tubules of control while reduces after both food and water deprivations. All types of spermatogenic cells were seen in control testis, while after water and food deprivations size of seminiferous tubules and spermatogenic cells population decreased. Scanning electron microscopic study exhibited fully mature sperms in clusters with head and elongated flagellum, whereas after water deprivation maximum sperms were distorted, scattered with highly reduced head. On food deprivation, only few sperms were seen with head and tail. Thus, taking into account the localization of ERα in testis, it is obvious that oestrogens produced locally are involved in regulation of spermatogenesis and spermiogenesis during stress.

Expression of estrogen receptor alpha in developing brain, ovary and shell gland of Gallus gallus domesticus: Impact of stress and estrogen

Estrogen plays a central role in the control of reproductive behaviour and in the regulation of neuroendocrine system. To elucidate the mechanism by which it controls the stress-modulated functions, it is important to understand how estrogenic effects are mediated. The distribution of estrogen receptor alpha (ERα) protein in brain, ovary and shell gland of chickens has been investigated. Immature chickens were taken and randomly divided into four groups. First group served as control (C), second water deprived for two days (WD), third treated with estradiol benzoate (E) and fourth treated with estradiol benzoate followed by water deprivation during last two days of treatment (E + WD). The dose of estradiol benzoate administered for 15 days was 0.5 mg/100 g. Immuno-fluorescent localization demonstrated the presence of ER alpha (ERα) in hypothalamic area, principally the pre-optic area on estrogen administration. However, ERα expression in brain decreased on water deprivation. ERα expression was observed highly in granulosa and thecal cells of E and E + WD ovary compared to immature while least on water deprivation. Similarly, ERα expression was abundant in tunica muscularis and epithelial cells of E and E + WD shell gland while lesser in WD. Plasma estradiol significantly increased in E and E + WD group while decreased on water deprivation. Plasma corticosterone decreased significantly in E and E + WD group while increased in WD. Therefore, we conclude that administration of estradiol in stress decreases corticosterone induced sensitivity mediated by an increased expression of ERα in brain, ovary and shell gland. It appears that negative feedback regulation is involved between HPA-axis and HPG- axis during stress in chickens.