Seasonal Expression Of Gonadotropin Receptors And Prolactin Receptor In Testis And Epididymis Of The Ground Squirrel(Citellus Dauricus Brandt)

Wild animals inhabiting temperate and high altitude experience acute seasonal changes in food,daylight hour and climate in an annual cycle,thus they held their reproductive activities in a more compatible period to mate and reproduce.During the process of seasonal breeding activities,sexual glands underwent distinct seasonal changes in morphology and/or function while testis and epididymis experience the most acute changes.In this research,we chose male wild ground squirrel as research model to investigate relations between seasonal changes of testis and epididymis and seasonal expression pattern of luteinizing hormone receptor(LHR),follicle stimulating hormone receptor(FSHR)and prolactin receptor(PRLR),and evaluated possible function of LHR,FSHR and PRLR in regulating seasonal morphological and functional changes in testis and epididymis of the wild ground squirrel.Histological and morphological results showed that parameters including weight,volume and lumen diameter of testis and epididymis were all significantly larger than during the breeding season.Immunohistochemical staining results in the testis revealed that LHR and FSHR were expressed in Leydig cells and Sertoli cells respectively,while PRLR was expressed in Leydig cells,Sertoli cells and germ cells.In the epididymis,LHR,FSHR and PRLR all expressed in the epithelial layer.As for the mRNA and protein expression,LHR,FSHR and PRLR were all higher during the breeding season in the testis.Similarly,FSHR,PRLR expression in caput,corpus and cauda epididymis as well as LHR expression in the caput and cauda epididymis showed high expression level in the breeding season.In addition,enzyme linked immunosorbent assay(ELISA)results revealed that serum concentration of luteinizing hormone,follicle stimulating hormone and prolactin in male wild ground squirrels peaked in the breeding season.These results indicate that testis and epididymis of male wild ground squirrel are target organs of luteinizing hormone,follicle stimulating hormone and prolactin and they may play pivotal roles in regulating seasonal changes of testicular and epididymal functions in the male wild ground squirrels.In summary,our study uncovers expression patterns of LHR,FSHR and PRLR in testis and epididymis of male wild ground squirrel.These findings provided preliminary knowledge about regulatory role of pituitary-derived hormone in regulation of reproductive function in wild seasonal breeing rodent species.