Morphological evidence of a permeability barrier in urodele testis

The testis of Triturus cristatus is multilobular and each lobe is composed of individual transient cysts in which Sertoli cells develop parallelly to the maturation of germ cells. The junctions between Sertoli cells in immature and mature cysts were studied with lanthanum used as a tracer and surface replicas. Immature cysts appeared as an "open" compartment, as they were penetrated by the tracer, and both sections and replicas showed that Sertoli junctions were differentiating. Mature cysts appeared as a "tight" compartment, as the tracer never reached the lumen and was stopped within inter-Sertoli specializations. Replicas evidenced ridges and grooves, coincident across face transition and continuous over a long distance around the surface of Sertoli membranes. These findings reinforce the idea that a barrier exists, regardless of the general organization of the gonad, and its establishment is related to the differentiation of the haploid male cells.