Abstract:

Abstract:Objective To investigate the influence of prepubertal exposure to estradiol benzoate (EB) in the male reproductive system of the rats and the natural process of tissue repair,and to clarify the possible mechanism of  the reproductive toxicity of exogenous estrogen.Methods Ninety 21-day-old male Wistar rats were randomly  divided into 2 experimental groups (low dose  of EB group and high dose of EB group,n=30) and  control group (n=30).The rats in the experimental groups were injected with  EB dissolved in peanut oil at 15（low dose of EB group） and 15 000 μg/kg（high dose of EB group） respectively,the rats in control group received equal vehicle injection only,once every other day for two weeks from postnatal day(PND)21 to 34.All of them were normally fed after the drug usage was stopped. The testes were harvested at the stages of PND 60 and PND 125(n=15 at each stage). The serum levels testosterone of (T),follicle-stimulating hormone(FSH),luteinizing hormone(LH),prolactin(PRL) and estradiol(E2) of the rats in various groups were detected with radioimmunology method and the weights of the rats in various groups were recorded;the histological changes of the testes tissue were observed with light microscope.Results On PND60,compared with control group,the T levels in low dose of EB group and high dose of EB group were decreased（P<0.05 or P<0.01）;the FSH,LH and E2 levels were increased (P<0.05 or P<0.01),and the PRL levels had no change（P>0.05）;the weights of testes were decreased(P<0.01);the histological  changes of the testes of the rats in experimental groups included seminiferous tubules maldevelopment,decreased cell number of seminiferous epithelia. Compared with low dose of EB group,the T and FSH levels in high dose of EB  group were decreased ( P<0.05 or P<0.01),the E2 and LH levels were increased( P<0.01),the  PRL level had no change（P>0.05）,and the weight of testes was decreased( P<0.01);the diameters of seminiferous tubules were smaller,there was no sperm in high dose  of EB group while there were a few sperms in low dose of EB group.On PND125,compared with control group,the T,FSH and PRL levels in low dose of EB group and high dose of EB group were decreased（P<0.01）,the E2 levels were increased (P<0.01);the LH level in low dose of EB group was increased（P<0.05）,the LH level in high dose of EB group was decreased（P<0.01）,and the weights of testes in high dose of EB group  were decreased(P<0.01); the diameters of seminiferous tubules and the cell number of seminiferous epithelia were increased but not apparent change. Compared with low dose of EB group,the T,LH levels in high dose of EB group were decreased (P<0.01),the E2 and FSH levels were increased(P<0.01),the PRL level had no change（P>0.05）,and the weight of testes was decreased(P<0.01);there was still no sperm in high dose of EB group,the number of sperms was increased in low dose of EB group,but it was  still lower  than that in control group.Conclusion EB is harmful to the reproductive system and can change the normal serum sex hormone levels,even  induces the irreversible injury.

Key words: exogenous estrogen, testis; , prepubertal, rats,Wistar, spontaneous recovery