CYTOSKELETON IN SERTOLI CELLS OF THE MOSQUITO FISH (GAMBUSIA-AFFINIS HOLBROOKI)

Background: There is little information about the distribution of cyto skeletal components in the testes of teleost fish. The aim of this pap er was to know the distribution of some major cytoskeletal proteins (t ubulin, actin, vimentin, desmin, and cytokeratins) in the Sertoli cell s of Gambusia affinis holbrooki and in their efferent duct epithelial cells which are possibly originated from the Sertoli cells. Methods: L ight and electron microscopic immunocytochemical studies and Western b lotting analysis were performed in G. affinis testis. Results: Actin i mmunoreaction was observed in the Sertoli cells at all spermatogenic s tages, although the intensity of this reaction varied from one stage t o another. Sertoli cells that support spermatogonia or spermatocytes s howed a weak immunoreaction which was uniformly distributed throughout the cytoplasm and somewhat more concentrated at the level of the inte r-Sertoli specialized junctions. Immunoreaction to actin increased dur ing the first stages of spermiogenesis and was mainly localized beneat h the plasma membrane. This immunoreaction was more intense in the bas al than in the apical cytoplasm of Sertoli cells. In a more advanced s tage of spermiogenesis, actin immunoreaction become stronger in the ap ical cytoplasm where Sertoli cells displayed cytoplasmic projections a round each spermatid. After sperm release, the apical Sertoli cell cyt oplasm still showed an intense actin immunoreaction. Intense immunorea ction to actin was also observed in the epithelial cells lining the ef ferent ducts. Immunoreaction to tubulin was diffuse throughout the Ser toli cell cytoplasm. No immunoreaction to vimentin or desmin was obser ved in the Sertoli cells during the spermatogenic process. Immunoreact ion to both vimentin and desmin was observed in the efferent duct cell s. Desmin immunoreaction was also observed in the seminiferous tubule boundary cells, mainly in the sections showing germ cell cysts at the last stages of spermiogenesis and in the peritubular cells that surrou nded the efferent duct epithelium. Immunoreaction to cytokeratins was found in the endothelium of testicular blood vessels but not in the Se rtoli cells or in the efferent duct epithelium. Conclusions: Immunorea ction pattern to cytoskeletal proteins in the Sertoli cells of G. affi nis differs from that reported in mammalian Sertoli cells. These diffe rences include the distribution of actin filaments and the absence of detectable vimentin immunoreaction in G. affinis Sertoli cells. (C) 19 95 Wiley-Liss, Inc.