S-100 protein immunoreactivity in mammalian testis and epididymis

The present study deals with immunohistochemical localization of S-100 protein in mouse, bank vole and pine vole testis and epididymis. S-100 protein immunoreactivity was observed in the endothelia of capillaries and lymphatic sinusoids of pine vole testis. A reaction to S-100 protein of the same intensity as that noted in the endothelia of testicular capillaries was found in myoid cells of pine vole and bank vole seminiferous tubules. Moreover, a positive reaction to S-100 protein was observed in bank vole and mouse Leydig cells. In the epididymis, a weaker reaction to S-100 occurred in smooth muscles of pine vole and mouse epididymal duct. Despite difficult interpretation of physiological role of S-100 protein we suggest that it may be a part of the blood-testis barrier. It may also participate in the processes of transcytosis and contractility; its cellular expression is regulated by local factors. However, location of S-100 is not specific to the representatives of the same order.