The blood-testis barrier in vertebrates having different testicular organization

Summary The occurrence of tight junctions between Sertoli cells, providing the structural basis of the blood-testis barrier, has been studied using hypertonic fixative and lanthanum tracer in the testes of seven species of vertebrates having different testicular organization. In all cases inter-Sertoli tight junctions, establishing an effective barrier, appear either when meiosis is complete (teleosts and amphibians, both with cystic testes) or immediately after the onset of meiosis (reptiles and birds, both having testes consisting of seminiferous tubules). In the cystic testes, tight junctions are regularly associated with desmosomes, whereas in testes with seminiferous tubules, cisternae of the endoplasmic reticulum are present beneath the junctions (subsurface cisternae). The avian testes examined have, in addition, septate-like junctions between the Sertoli cells but before the tight junctions.Dedicated to Prof. Dr. H. Rollhäuser, Münster, on the occasion of his 65th birthday.