外源性雌激素对雄性青春前期大鼠生殖系统的损伤及其自然修复过程

目的: 研究雄性大鼠青春前期灌胃摄入外源性雌激素苯甲酸雌二醇（EB）对生殖系统发育的影响及停止干预后机体自然修复情况，阐明外源性雌激素产生生殖毒性的可能机制。方法:选择21日龄雄性Wistar大鼠90只，随机分为对照组、低剂量EB组和高剂量EB组，每组30只。于青春前期，即出生后第21天（PND21）时低剂量EB组和高剂量EB组分别灌胃给予15和15 000 μg?kg-1 EB，对照组仅给予等剂量的溶媒花生油，隔日1次，连续给药2周，停药后正常饲养，于性成熟期（PND60）及自然恢复65 d（PND125）时分批从每组中随机抽取15只大鼠处死取材，放射免疫法检测大鼠血清卵泡刺激素（FSH）、黄体生成素（LH）、催乳素（PRL）、睾酮（T）和雌二醇（E2）水平，称量睾丸质量，光学显微镜观察睾丸组织形态学表现。结果: 染毒2周后饲养至生后60 d解剖大鼠，与对照组比较，低和高剂量EB组大鼠血清T水平均降低（P<0.05或P<0.01）,FSH、LH及E2水平均升高 (P<0.05或P<0.01),PRL水平无明显变化（P>0.05），睾丸质量均下降（P<0.01）；睾丸组织切片可见睾丸生精小管排列欠致密，小管间隙增大，生精上皮中生精细胞层数减少。与低剂量EB组比较,高剂量EB组大鼠血清T和FSH水平降低(P<0.05或P<0.01)，E2和LH水平升高( P<0.01)，PRL水平无明显变化（P>0.05），高剂量睾丸质量降低(P<0.01)；睾丸组织切片可见管径较小，高剂量EB组未见精子，低剂量EB组可见少量精子。经自然恢复65 d后，与对照组比较，低和高剂量EB组大鼠血清T、FSH和PRL水平均降低(P<0.01)，E2水平升高( P<0.01)；低剂量EB组大鼠血清LH水平升高（P<0.05）；高剂量EB组大鼠血清LH水平降低(P<0.01)，睾丸质量降低（P<0.01），睾丸组织切片可见管径较恢复前无明显变化，生精细胞层数较恢复前增多，但仍少于对照组；与低剂量EB组比较，高剂量EB组大鼠血清T和LH水平降低（P<0.01），FSH和E2水平升高（P<0.01），PRL无明显变化（P>0.05），睾丸质量降低（P<0.01）；睾丸组织切片可见生精小管，与恢复前比较无明显变化，高剂量EB组仍未见成熟精子细胞,低剂量EB组可见精子数较恢复前增多，但仍少于对照组。结论: 外源性雌激素可导致血清性激素分泌紊乱和生殖系统损伤，严重时甚至可引起不可逆损伤。

Injury of male reproductive system of rats by prepubertal exposure to exogenous estrogen and its natural process of tissue repair

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 2experimental 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 000μg·kg-1(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)21to 34.All of them were normally fed after the drug usage was stopped.The testes were harvested at the stages of PND 60and PND 125(n=15at 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<0.05or P<0.01);the FSH,LH and E2levels were increased(P<0.05or 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<0.05or P<0.01),the E2and 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 E2levels 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 E2and 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.