Reversible effect of testosterone undecanoate injection on spermatogenesisin rats

Aim: To study the effect of testosterone undecanoate (TU) injection on sper matogenesis in rats. Methods: Twenty adult SD rats received vehicle or TU ( 8 mg/kg, 19 mg/kg or 625 mg/kg) injection, im, every 15 days for 60 days, a nd another 38 animals received similar treatments for 130 days with half of them undergoing a recovery phase of 120 days (5 rats for each treatment). At the end of the treatment, testes were removed and the diameter of the se miniferous tubules and the number of late elongated spermatids (steps 15 - 19) per testis were estimated with stereological methods as a measure of th e spermatogenic efficiency. Results: Low dose (8 mg/kg) TU treatment virtua lly had no effect on spermatogenesis. A dose of 19 mg/kg slightly suppresse d spermatogenesis 60 days after treatment, and severe suppression occurred after another 70 days of dosing. Spermatogenesis was completely recovered a t the end of the recovery phase. Large dose (625 mg/kg) TU treatment did no t significantly affect spermatogenesis and was well tolerated by animals. C onclusion: TU injection reversibly suppresses spermatogenesis in rats.