RESUMEN
OBJECTIVE: To investigate the incidence and spermatogenesis of cryptorchid testes induced by postnatal injection of estradiol. METHODS: Ninety male newborn Balb/C mice were randomly divided into an experimental (n = 60), a solvent control (n = 20) and a normal control group (n = 10). The experimental mice were again assigned to a 4-week, a 6-week, an 8-week, and a 10-week subgroup, and injected subcutaneously with 17-beta estradiol (5 microg/d) from 3 to 28, 3 to 42, 3 to 56 and 3 to 70 days after birth, respectively. The incidence of cryptorchidism and morphological changes of the testes were observed at 2 weeks after drug withdrawal. RESULTS: The incidence rates of cryptorchidism in the 4-, 6-, 8- and 10-week groups were 0%, 26.7%, 60% and 60%, respectively, but no cryptorchidism occurred in the solvent and normal control groups. The 4- and 6-week groups showed autonomous descent of the cryptorchid testes and recovery of spermatogenesis after drug withdrawal. The models became stable and no spermatogenesis recovery was observed after 8 weeks of continuous medication. CONCLUSION: Stable cryptorchid infertile models can be established in mice by postnatally continuous injection of estradiol for over 8 weeks.