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-c ell contacts within the rat seminiferous epithelium was investigated, Double fluorescence experiments using phalloidin staining of actin fil aments and anti-integrin subunit antibodies showed that the receptor b elongs to the Sertoli cell lateral domains engaged in the characterist ic 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 epitheli um of aspermatogenic testes, obtained through X-irradiation in utero ( Sertoli-cell-only testes), at the level of inter-sertoli junctions bot h ES and alpha 6 beta 1 integrins are present, In order to study the d ependence of alpha 6 beta 1 receptors and ES formation upon FSH stimul ation during development, 9-day-old testes were grown in organ culture in basal as well as FSH-supplemented conditions, FSH stimulation, whi ch is necessary for the progression of spermatogenesis to early meioti c stages, appears to be required for the development of inter-Sertoli junctional structures containing ES and alpha 6 beta 1 integrins, Thes e observations indicate that the receptor belongs to the inter-Sertoli junctional machinery and that its expression at that level is not dep endent on active spermatogenesis but requires FSH stimulation.