Correlation between blood-testis barrier development and onset of the first spermatogenic wave in normal and in busulfan-treated rats: a lanthanum and freeze-fracture study.

Pregnant rats (day 13) received 10 mg/kg of Busulfan i.p. The seminiferous tubules of their offspring from post-natal age 1 day up to day 35 were examined with TEM after fixation plus intercellular tracers, and with freeze-fracture techniques. During this period, the inter-Sertoli tight junctions of controls increase both in number and in length. Between days 10 and 13 the seminiferous cords have numerous preleptotene and leptotene spermatocytes surrounded by tracer. The inter-Sertoli junctions are tortuous and predominantly perpendicular to the basal lamina. Between ages 13 and 20 days the seminiferous epithelium reaches zygotene-pachytene stages. The tracer is stopped at the inter-Sertoli junctions at this stage, whereas it still permeates tubules displaying preleptotene and leptotene spermatocytes. Freeze-fracture shows that the orientation of inter-Sertoli junctions has changed to parallel, both to each other and to the basal lamina. In the Busulfan-treated rats, the tubules continue having, up to post-natal day 30, only Sertoli cells and scanty spermatogonia. In these, lanthanum penetration goes as far as the apical Sertoli cell region; the inter-Sertoli junctions still show tortuous strands, and most are oriented perpendicular to the basal lamina. This indicates that formation of the first competent inter-Sertoli junctions is temporo-spatially simultaneous with the appearance of zygotene-pachytene spermatocytes.