Seasonal Expressions Of The Reproductive Hormones' Receptors In The Uterus Of The Wild Daurian Ground Squirrel(Spermophilus Dauricus)

The reproductive activities of wild mammals living in temperate regions change periodically with the seasons due to the change of light and other environmental conditions,with obvious difference between the breeding and the non-breeding seasons.In order to explore the reproductive characteristics of wild mammals,it is particularly important to study the ways and mechanisms of their seasonal reproduction.Therefore,this study used the wild Daurian ground squirrel(Spermophilus dauricus),a typical seasonal reproductive wild animal,as the research model to explore the relationship between the expression level changes and the seasonal changes of uterus and androgen receptor(AR),two estrogen receptors(ERa and ER?),P450 aromatase(P450arom),Luteinizing hormone receptor(LHR)and follicle-stimulating hormone receptor(FSHR)in breeding season(April)and the non-breeding season(June),to evaluate the possible role of the AR,ERs,LHR and FSHR in regulating the seasonal changes of uterine morphology and function in the wild Daurian ground squirrels.The morphological results showed that the weight and volume of uterus in the breeding season were larger than that in the non-breeding season,and the ratio of uterine weight to body weight in the breeding season was significantly higher than that in the non-breeding season.Histological results showed that the uterine endometrium thickness and the number of uterine glands in the reproductive period were significantly greater than those in the non-reproductive season.Immunohistochemical results showed that ERa and ER? were expressed in the nucleus of uterine stromal cells and uterine gland cells during the breeding and non-breeding seasons,and P450arom was only expressed in the cytoplasm of uterine gland cells,and the immunostaining was significantly stronger in the breeding season than it in the non-breeding season.AR was only expressed in the nucleus of uterine stromal cells during the breeding and non-breeding season with stronger positive staining in the non-breeding season than it in the non-breeding season.LHR was expressed in the cytoplasm of uterine stromal cells at the breeding season and in the cytoplasm of stromal cells and glandular cells at the non-breeding season,while FSHR was expressed in the cytoplasm of stromal cells and glandular cells at both seasons,and the positive staining was stronger at the breeding season than the non-breeding season.In the uterus,western blot and RT-qPCR results showed that the protein expression and mRNA levels of AR were higher in the non-breeding season than in the breeding season,while the protein and mRNA levels of other hormone receptors were higher in the breeding season than in the non-breeding season.In addition,mRNA levels of ER?,ER?,LHR and FSHR were positively correlated with uterine weight,while mRNA levels ofAR were negatively correlated with uterine weight.The results showed that the plasma levels of 17?-estradiol,progesterone,LH and FSH were higher in the reproductive period than in the non-reproductive period.The above results indicated that the seasonal changes in the expression levels of AR,ERs,P450arom,LHR and FSHR may be related to the changes in uterine morphology and histology,and may play an important endocrine or autocrine/paracrine role in the regulation of uterine function in wild Daurian ground squirrel.