Seasonal Changes In Morphology And Immunoreactivity Of PDGFs In The Epididymis Of Wild Ground Squirrels(Citellus Dauricus Brandt)

The wild ground squirrel is a typical seasonal breeder. Our previous results have shown seasonal changes in testicular weight and size and seminiferous tubule diameter of wild ground squirrels are correlated with changes in spermatogenesis. However, to our knowledge, there are few studies focusing on the seasonal variation of the epididymis of wild rodents. The epididymis was known as the most complex exocrine glands, it is accessory male glands in mammals. It is only during transit through the epididymis that spermatozoa undergo maturation and acquire progressive motility and the ability to fertilize ova. So the epididymis plays an important role in male reproduction. Our results showed, similar with the testis, the epididymis has also shown the characteristic of seasonal variation. To have a further study in this variation, therefore, this study provides a detailed morphological description of the wild ground squirrel’s epididymis (cell types and segments) and a qualitative as well as quantitative characterization of the seasonal changes in the different parts of the duct. Moreover, we also detected the immunolocalization and immunoreactivity of PDGF-A, PDGFR-a, AR, ERs and P450aromatase by immunohistochemistry and western blotting. The results showed, there are distinctive seasonal morphological variations between breeding and nonbreeding season. The highest value for epididymal length was found during the breeding season in May (mean value=20.37±1.00mm), and the lowest value was found during the nonbreeding season in July (mean value=8.09±0.68mm). In breeding season, the epithelial height and the lumen diameter achieve to the highest level and lots of sperm were found in the lumen whereas in the nonbreeding season it shrink to lowest level and no sperm were found in lumen. Moreover, the proportions of the three compartments (interstitial tissue, epithelium and lumen of the duct) revealed distinct variances. The immunological result shows, Strong immunostaining of PDGF-A was present in the myoid cell and on the sperm in the breeding season, whereas there was a faint signal in the myoid cell in the nonbreeding season. PDGFR-a was expressed in all cell types of the epithelium throughout the whole seasonal cycle, and immunostaining of PDGFR-a in the breeding season was significantly stronger compared with that of the nonbreeding season. PDGF-B was not detected in the epididymis of wild ground squirrels. AR and ERahave strong positive signal in both breeding and nonbreeding seasons, and more cytoplasm staining detected in nonbreeding season. ER(3only detected in the breeding seasonal in sperm. Immunostaining of P450aromatase in the breeding season was significantly stronger compared with that of the nonbreeding season. These results suggested that seasonal morphological changes in epididymis were correlated with immunoreactivities of PDGF-A and its receptor PDGFR-a and that PDGF-A and PDGFR-a might function as paracrine, autocrine or apocrine factors mediating the action of steroid hormones in the wild ground squirrel epididymis.