Expression And Effects Of GnRH And LH On Corpus Luteum Of Pregnant Sows

The hypothalamus-pituitary gonadal axis(HPG)is the key to mammalian reproductive regulation,the hypothalamus GnRH secretion via the portal circulation reached the adenohypophysis,which is the main target organs,GnRH reached the adenohypophysis after GnRH and its specific receptors stimulated gonadal hormone synthesis and release of LH and FSH,LH and FSH reached by the bloodstream gonad organs such as testis and ovary adjusting the body reproductive activity.In recent years,studies have found that GnRH is also distributed and expressed in many tissues of extra-hypothalamus,and LH is also widely present in the tissues of extra-pituitary,suggested that GnRH and LH have a more extensive physiological regulation role in the body.GnRH,LH and their receptors also exist in corpus luteum of mammals,and they have direct regulatory effects on ovarian function.These studies mainly focus on corpus luteum of estrus cycle.However,so far,studies on the expression and effects of GnRH and LH in corpus luteum of gestation sows have not been reported.In this study,Real-time RT-PCR and immunohistochemistry were used to detect the distribution and expression of GnRH and LH in corpus luteum of sows at different stages of gestation.Then,GnRH and LH were used to separately treat pregestation luteal cells cultured in vitro,to explore the regulatory effects of GnRH and LH on progesterone secretion in luteal cells,as well as the effects of GnRH on LH secretion and mRNA in luteal cells,and the influence of LH on GnRH secretion and mRNA in luteal cells.The results are as follows:1.Real-time RT-PCR results showed that the distribution of GnRH mRNA was observed in the corpus luteum of sows at different stages of gestation,and the levels in the early and middle gestation were significantly higher than those in the later gestation(P < 0.05).There was no significant difference between the early and the middle gestation(P > 0.05).Immunohistochemical staining results showed that GnRH was widely expressed in the corpus luteum of sows at different stages of gestation,mainly located in the cytoplasm of luteal cells,and almost all luteal cells were GnRH immuno-positive.2.LH mRNA was distributed in the corpus luteum of sows at different stages of gestation,with the lowest level in the later gestation,significantly lower than that in the early and the middle gestation(P < 0.05),and there was no significant difference between the early and the middle gestation(P > 0.05).The distribution and expression of LH in corpus luteum of sows at different stages of gestation were consistent with the distribution and expression characteristics of GnRH.LH was expressed in corpus luteum of sows at different stages of gestation,and positive LH immunological responses were found in cytoplasm of luteal cells in the early,midlde and later gestation.3.Treatment of luteal cells with different concentrations of GnRH showed that GnRH promoted the secretion of progesterone in luteal cells by dose-dependent manner.Compared with the blank control group,GnRH treatments of 10 pg/mL,100 pg/mL,1000 pg/mL and 10000 pg/mL significantly increased the concentration of progesterone in the medium(P < 0.05).The results showed that 1 pg/mL,10 pg/mL,100 pg/mL,1000 pg/mL and 10000 pg/mL treatment could significantly increase the level of LH mRNA and secretion in luteal cells(P < 0.05).4.The results of treating luteal cells with LH at different concentrations showed that 0.001 U/mL,0.01 U/mL,0.1 U/mL and 1 U/mL could significantly promote the synthesis and secretion of progesterone in luteal cells(P < 0.05).Treatment with LH at 0.1 U/mL and 1 U/mL significantly increased the level of GnRH mRNA and secretion.This study found that GnRH and LH mRNA were distributed in corpus luteum of sows at different stages of gestation,and their level of expression were consistent with functions of corpus luteum during gestation.GnRH and LH were expressed in corpus luteum of sows at different stages of gestation,mainly located in the cytoplasm of luteal cells.GnRH can promote the secretion of progesterone and LH by a dose-dependent manner.LH can increase the level of GnRH mRNA and promote the secretion of progesterone and GnRH.The results showed that the corpus luteum of gestation sows had the ability to produce and secrete GnRH and LH,and the secreted GnRH and LH of corpus luteum of gestation regulated the corpus luteum function of gestation by autocrine/paracrine manner.