Immunohistochemical distribution of S-100 protein and subunits (S100-α and S100-β) in the swamp-type water buffalo (Bubalus bubalis) testis

The distribution and localization of S‐100 protein (S‐100) and its subunits (S100‐α and S100‐β) in the testis of swamp‐type water buffalo were investigated using immunohistochemistry. S‐100 was detected in the Sertoli cells in the convoluted seminiferous tubules, modified Sertoli cells lining the terminal segment of the seminiferous tubules and in the intratesticular excurrent ducts (straight tubules and rete testis). S100‐β showed the same distribution and localization with that of S‐100. However, the cytoplasmic extension of the Sertoli cells in S100‐β staining showed less staining intensity compared with that of S‐100. S100‐α showed a positive staining only in the modified Sertoli cells of the terminal segment of the seminiferous tubule. Endothelial cells of blood vessels were also positive with the proteins while the Leydig and spermatogenic cells showed a negative reaction. The localization of S‐100 in the testis of the water buffalo was in parallel with that of other artiodactyls which supports the hypothesis that this protein is a multifunctional protein. S100‐β in the Sertoli cells suggests that this protein is involved in establishing blood–testis barrier. Its presence in the modified Sertoli cells and in the epithelium of the excurrent ducts suggest secretory and absorptive function, respectively. Meanwhile, S100‐α, which was detected only in the modified Sertoli cells, is involved in the secretory activity of these cells that are related to exocrine function.