Seasonal Changes in Spermatogenesis and Immunolocalization of Cytochrome P450 17α-Hydroxylase/c17-20 Lyase and Cytochrome P450 Aromatase in the Wild Male Ground Squirrel (Citellus dauricus Brandt)

The purpose of this study was to investigate seasonal changes of spermatogenesis and the cellular localization of P450c17 and P450arom in wild male ground squirrels during the breeding and non-breeding seasons. The testicular weight, testicular size and score count of spermatogenesis from April to September were measured, and histological and immunohistochemical observations of testicular tissues were performed in wild male ground squirrels. In addition, total proteins were extracted from testicular tissue in the breeding and non-breeding seasons and were used for Western blotting analysis for P450c17 and P450arom. There were marked variations in testicular weight, testicular size and score count of spermatogenesis from the breeding season (April) to the non-breeding season (September). Histologically, spermatogonia, primary spermatocytes, secondary spermatocytes and spermatozoa were identified in the breeding season (April). Immunolocalization of P450c17 was detected in Leydig cells and spermatozoa during the breeding season and was only found in Leydig cells during the non-breeding season. The positive signals of P450c17 by Western blotting were both observed in the breeding and non-breeding seasons. Immunolocalization of P450arom was observed in Leydig cells, Sertoli cells and all types of spermatogenic cells including mature-phase spermatozoa in the breeding season, while immunoreactivity for P450arom was not present in the testis of the non-breeding season. With P450arom antibody, a band was also only detected in the breeding season by Western blotting. These results suggest that the seasonal changes in testicular weight and size are correlated with spermatogenesis and immunolocalization of P450c17 and P450arom, and androgen and estrogen may play an important role in the spermatogenesis and testicular recrudescence and regression process.