Junctional contacts between Sertoli cells in normal and aspermatogenic rat seminiferous epithelium contain (alpha)6(beta)1 integrins, and their formation is controlled by follicle-stimulating hormone

The distribution of (alpha)6(beta)1 integrins at the level of cell-to-cell contacts within the rat seminiferous epithelium was investigated. Double fluorescence experiments using phalloidin staining of actin filaments and anti-integrin subunit antibodies showed that the receptor belongs to the Sertoli cell lateral domains engaged in the characteristic junctional structures known as ectoplasmic specializations (ES), at the level both of inter-Sertoli junctions and of the contacts between Sertoli cells and elongating spermatids. In the seminiferous epithelium of aspermatogenic testes, obtained through X- irradiation in utero (Sertoli-cell-only testes), at the level of inter- Sertoli junctions both ES and (alpha)6(beta)1 integrins are present. In order to study the dependence of (alpha)6(beta)1 receptors and ES formation upon FSH stimulation during development, 9-day-old testes were grown in organ culture in basal as well as FSHsupplemented conditions. FSH stimulation, which is necessary for the progression of spermatogenesis to early meiotic stages, appears to be required for the development of inter-Sertoli junctional structures containing ES and (alpha)6(beta)1 integrins. These observations indicate that the receptor belongs to the inter-Sertoli junctional machinery and that its expression at that level is not dependent on active spermatogenesis but requires FSH stimulation.