Single administration of di(n-butyl) phthalate delays spermatogenesis in prepubertal rats

Morphological alterations in seminiferous tubules caused by single administration of di(n-butyl) phthalate (DBP) in 3-week-old rats were investigated throughout the first wave of spermatogenesis. Single administration of DBP (500 mg/kg) showed progressive detachment and displacement of spermatogenic cells and disappearance of tubular lumen at 3 h after treatment, and then showed thin seminiferous epithelia and wide tubular lumen at day 1 (D1). At D1, quite significant numbers of apoptotic spermatogenic cells were detected, and then they gradually decreased in accordance with the passage of time. In contrast, the testes revealed lower weight gain, even after completion of first wave of spermatogenesis in the DBP-treated group, compared to the control. In order to clarify whether spermatogenic cells differentiate into mature spermatids in the DBP-treated rats, immunohistochemical staining for Hsc 70t, a specific marker for elongate spermatids, was carried out. As a result, the decrease in mature spermatids in the DBP-treated testes, compared to the control, was demonstrated. For example, at D20 (41-day-old) after treatment, the most advanced spermatids in the tubules from rats in the DBP-treated groups were steps 2–4, while those of the control were steps 12–13. Moreover, in some tubules, pachytene spermatocytes were the most advanced spermatogenic cell. At D30 (51-day-old) after treatment, maturation of spermatogenic cells in the DBP-treated rats proceeded further, and the most advanced spermatids in tubules were steps 8–9, while those of the control were steps 15–19. These results lead us to the postulation that a single administration of DBP to prepubertal rats delays maturation of spermatogenic cells, even after completion of first wave of spermatogenesis.