The present work examined the expression for both estradiol-17β subtype α (ERα) and GnRH receptors (GnRH-R) and that for FSHβ as well as their regulation after two-days of fasting in the anterior pituitary gland of control and estrogen-primed rabbits, together with the LH dynamic secretion following GnRH stimulation. Sexually mature unmated NZW female rabbits were randomly assigned to the following groups: control does fed ad libitum (AL), AL implanted with 2.0 mg estradiol-17β (AL-E), 48 h fasted does (F), and F implanted with estrogens (F-E). Whereas control does were fed ad libitum, treated does were fasted for 48 h before killing or i.m. GnRH injection. Immediately after GnRH treatment, fasted does were re-fed ad libitum. ERα immunoreactivity was evidenced in the nucleus of most pituitary cells in both control and treated does. In F-E rabbits, the intensity of ERα signal and the number of positive cells were markedly reduced. Positive staining for GnRH-R was evidenced in the nucleus and in the cytoplasm, although with weaker signal, of many pituitary cells of both control and treated does. In pituitaries of F-E does, GnRH-R signal intensity was markedly reduced. Fasting and oestrogen did not affect basal plasma LH concentrations. In all the groups, the LH peak surge was observed 30 min after GnRH injection. The LH magnitude was lower (P≤0.01) in F than in AL rabbits, but higher (P≤0.01) in F-E than in AL-E does. In all the groups, plasma LH levels declined close to basal values 4 h after GnRH. Fasting as well as oestrogen priming of both AL and F rabbits reduced (P<0.01) the levels of pituitary ERα mRNA expression. The lowest ERα gene expression was found in F-E does. GnRH-R mRNA relative abundance was down regulated (P<0.01) four-fold in F-E does. FSH mRNA expression was down-regulated (P<0.01) only in F-E rabbits. In conclusion, the rabbit anterior pituitary responds to changes in nutritional status, as provoked by 48 h fasting, and to gonadal steroid through adjustments of ERα, GnRH-R, and FSHβ at the level of gene expression as well as through regulations of LH release into the blood stream in order to adjust the reproductive system to metabolic condition. Complete deprivation of food for a short period of time could be a useful model for analysing the interrelationships between nutritional factors and reproductive function in rabbits.

Pituitary gonadotropins and receptors for estrogen and GnRH in fasted does / C. Boiti, G. Galeati, M. Maranesi, L. Lilli, L. Murgiano, G. Brecchia, C. Dall'Aglio, F. Mercati, A. Gobbetti, M. Zerani (PROCEEDINGS WORLD RABBIT CONGRESS). - In: Proceeding World Rabbit Congress[s.l] : S.n., 2008 Jun. - ISBN 9788890281464. - pp. 285-289 (( Intervento presentato al 9. convegno World Rabbit Congress tenutosi a Verona nel 2008.

Pituitary gonadotropins and receptors for estrogen and GnRH in fasted does

G. Brecchia;
2008

Abstract

The present work examined the expression for both estradiol-17β subtype α (ERα) and GnRH receptors (GnRH-R) and that for FSHβ as well as their regulation after two-days of fasting in the anterior pituitary gland of control and estrogen-primed rabbits, together with the LH dynamic secretion following GnRH stimulation. Sexually mature unmated NZW female rabbits were randomly assigned to the following groups: control does fed ad libitum (AL), AL implanted with 2.0 mg estradiol-17β (AL-E), 48 h fasted does (F), and F implanted with estrogens (F-E). Whereas control does were fed ad libitum, treated does were fasted for 48 h before killing or i.m. GnRH injection. Immediately after GnRH treatment, fasted does were re-fed ad libitum. ERα immunoreactivity was evidenced in the nucleus of most pituitary cells in both control and treated does. In F-E rabbits, the intensity of ERα signal and the number of positive cells were markedly reduced. Positive staining for GnRH-R was evidenced in the nucleus and in the cytoplasm, although with weaker signal, of many pituitary cells of both control and treated does. In pituitaries of F-E does, GnRH-R signal intensity was markedly reduced. Fasting and oestrogen did not affect basal plasma LH concentrations. In all the groups, the LH peak surge was observed 30 min after GnRH injection. The LH magnitude was lower (P≤0.01) in F than in AL rabbits, but higher (P≤0.01) in F-E than in AL-E does. In all the groups, plasma LH levels declined close to basal values 4 h after GnRH. Fasting as well as oestrogen priming of both AL and F rabbits reduced (P<0.01) the levels of pituitary ERα mRNA expression. The lowest ERα gene expression was found in F-E does. GnRH-R mRNA relative abundance was down regulated (P<0.01) four-fold in F-E does. FSH mRNA expression was down-regulated (P<0.01) only in F-E rabbits. In conclusion, the rabbit anterior pituitary responds to changes in nutritional status, as provoked by 48 h fasting, and to gonadal steroid through adjustments of ERα, GnRH-R, and FSHβ at the level of gene expression as well as through regulations of LH release into the blood stream in order to adjust the reproductive system to metabolic condition. Complete deprivation of food for a short period of time could be a useful model for analysing the interrelationships between nutritional factors and reproductive function in rabbits.
ERα; GnRH-R; Gonadotropins; Fasting; Pituitary
Settore VET/02 - Fisiologia Veterinaria
giu-2008
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/688220
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