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

Abstract

The distribution and localization of S-100 protein (S-100) and its subunits (S100-alpha and S100-beta) 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-beta showed the same distribution and localization with that of S-100. However, the cytoplasmic extension of the Sertoli cells in S100-beta staining showed less staining intensity compared with that of S-100. S100-alpha 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-beta 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-alpha, which was detected only in the modified Sertoli cells, is involved in the secretory activity of these cells that are related to exocrine function.

Localization of S-100 proteins in the testis and epididymis of poultry and rabbits

“…In the testis of roosters, pigeons, and rabbits, the S-100 was generally localized in the cytoplasm and nucleus of Sertoli cells. These findings are consistent with numerous approaches (Table 2) that investigated the localization of S-100 in the testis of several mammalian species including bovine [20, 21, 22], sheep [21], rat [21, 24], cat [21, 26], ram, boar, horse, dog [20, 21], buffalo [27], monkey [29], and human [24, 30]. Although the exact testicular function of S-100 is yet unclear, it is striking to note that the bulk of the cell types staining positive for S-100 exhibit special morphological features [24] such as Sertoli cells [20].…”

“…S-100 protein in the Sertoli cells is assumed to be involved in the microtubule assembly-disassembly system [29]. Further on, the protein may play a role in the secretory and absorptive functions and may be involved in establishing the blood-testis barrier [21, 27]. Nevertheless, S-100 was not localized to Sertoli cells of the Sudani ducks.…”

“…Similarly, endothelial cells of capillaries, veins, and lymphatic vessels are regularly S-100 protein immunoreactive in rat, boar, ruminants, European bison, and human [20, 21, 24, 27, 33]. No expression of S-100 was seen in germ, Leydig, and myofibroblast cells of birds and rabbits.…”

“…Although a wide variety of diverse functions have been attributed to S-100 proteins, their exact biological role in the epididymis is still not known. S-100 is involved in the absorptive and secretory functions in the intra-testicular excurrent duct system [21, 27]; it may promote similar tasks in the extra-testicular excurrent duct system. S-100 has been associated with several activities including regulation of the diffusion of monovalent cations across membranes and modulation of the physical state of membranes [14].…”

“…Despite all of these proposed functions, the exact biological role of this protein in the testis and epididymis is not yet known. The localization of S-100 was investigated in the testis and epididymis of several mammalian species including bovine [20, 21, 22, 23], sheep [21], rat [21, 24, 25], cat [21, 26], ram, boar, horse, dog [20, 21], buffalo [27, 28], monkey [29], and human [24, 30]. Conversely, one report concerning the S-100 localization in the testis and epididymis of adult White Peking ducks is, to our knowledge, available [31].…”