Multilayered structure of the basal lamina of the tubuli recti in normal mice.

Previous studies have demonstrated that the blood-testis barrier (BTB) at the tubuli recti (TR) and the rete testis (RT) is less complete than at the seminiferous tubules (ST). However, there has been no report focusing on the basal lamina, which is an important component of the BTB at both TR and RT. In the present study, we performed electron microscopic observation of the basal lamina at the TR and RT, in comparison with that of those of the ST in normal mice. The results showed that the basal lamina of modified Sertoli cells at the TR segment exhibited a wavy and multilayered structure, but the Sertoli cells of ST and the epithelium of RT had an almost flat and single-layered basal lamina. It was also noted that wide gaps existed between the modified Sertoli cells, the basal lamina of the epithelial layer, and the myoid cell layer at the middle TR segment. This characteristic structure of the basal lamina of the TR epithelial layer may be one of the factors for its incomplete BTB.