Effects Of Methoxychlor On Female Gonad Toxicities And Possible Mechanisms In Rats

There are many kinds of chemicals which can simulate or interfere endocrine function of human beings in nature environment, such as synthesis, secretion, transportation, binding, action and so on. Metabolism or elimination of natural blood-borne hormones in the body were influenced, which resulted in changes in multiple aspects incluing reproduction, growth and behaveior. These kinds of conpounds are defined as endocrine disruptor chemicals (DECs) which can cause serious influence to generateon health of mankind. Because the process of female's generation prodedure is more complicate than male's, there are much more research documents based on the influences caused by EDCs in male than female. women provides not only reproductive cells but also environment of foetus growth. For these reasons, it is very important to protect women's generational health.Methoxychlor (MXC) is an organochlorine pesticide, which is widely sprayed on fruits, vegetables, forage crops, and home gardens to prevent insects from attacking them. MXC is considered to be an alternative to dichloro-diphenyl-trichloroethane (DDT). Although MXC has been considered as a potent environmental toxicant for several years, it was not until recently that MXC had been considered to be a reproductive toxicant.Until rencently, numerous researches have found that MXC could cause damage to male rat's reproductive system. However, there is little information regarding influence of MXC on female reproductive activity. Consequently, the present study was designed to investigate the adverse effect of MXC on various reproductive parameters of female rat. The study was designed to analyze the effects of MXC on ovary and as well as expression of hormone receptor in both ovary and uterus. We also studied whether vitminE can reduce the reproductive toxicity of organic pollutants of MXC to female SD rats.Part 1. Construction of methoxychlor poisoned rats model and effects of methoxychlor on reproduction and endocrine system.Forty female SD rats were randomly divided into 4 groups, 4 different dose levels (0, 16, 32 and 64 mg/(kg?d) MXC ) were injected intraperitoneally accordingly for 20 d. Vaginal smears of rats were performed to determine estrous cycle. The rats were sacrificed on the day of estrus stage. Body weights, estrus stage, organ weights and organ coefficients of ovary were observed. Uterine tissue and ovary were prosessed for histologic examination. Serum follicle stimulating hormone(FSH), leteinizing hormone(LH), estradiol(E2) and progestereone(P) were detected with the radio immunoassays. Estrogen receptor in the uterine and ovary were examined with the SP immunohisochemical method. Expression of FSH in pituitary gland was detected with immunofluorescence. Ultrastruction changes of folliciles was observed by electron microscope. A quantitative analysis of different stage follicles, atretic follicles and corporaluteum were conducted. Results:①Increasing of body weight was not different between 4 groups after treatment.②E struation was prolonged in MXC 32 and 64 mg groups, periodicity decresed accordingly.③Organ weights and organ coefficients of ovaries in rats treated with MXC 32 and 64 mg groups were significantly different from the control group.④Serum follicle stimulating hormone (FSH) and estradiol (E2) were significantly decreased in 32, 64 MXC group. There were no significant differences on both serum progestereone (P) and leteinizing hormone (LH) in the 4 groups.⑤Numbers of atresic follicle were significantly increased in both the MXC 32 and 64 mg groups, the atresic rate of secondary follicle was significantly increasd.⑥There were no significant differences on the positive percentage of ER in both endometria of uterus and ovaries in the 4 groups.⑦The positive percentage of FSH in pituitary gland were desreased in rats treated with MXC 32 and 64 mg/(kg?d). Conclusion:①MXC could result in prolonged estruation circle and increased number of atresic follicle.②Hypothalamic-pituitary-ovarian axis function and expression of FSH level in pituitary gland were changed at the dose we used, that's why female gonads toxicities was caused. MXC in experimental dose may induce the disorder of hypothalamic-pituitary-ovarian axis and decrease the expression level of FSH, however, this dose can not change the expression level of ER secreted from ovarian and uterus, and increase the toxicities of female gonad.③N o significant influence on female gonads toxicities was found in low-dose group.Part 2. Effects of methoxychlor on the function of ovarian antioxidant system in ratsWe erected the model on intraperitoneal injection MXC just like the first experiment. Forty SD rats were randomly divided into 4 groups treated with MXC 0, 32,64 mg/(kg?d) and MXC 64 mg +VitE 20 mg/(kg?d) )for 20d. The activities of superoxide dismutase (SOD), reduced glutathione hormone (GSH) and the level of malondialdehyde (MDA) were measured by spectrophotometry. The method of reverse transcription polymerase chain reaction (RT-PCR) was used to detect the presence of antioxidase(SOD,GSH-Px,CAT) in rat ovaries, which may be helpful to elucidate the mechanism of endocrine disruption of MXC. Results:The activities of GSH and SOD in the MXC 32 and 64mg groups were decreased significantly as compared with those in the control group (P<0.05), but the level of MDA was raised in comparison with the control group (P<0.01). The expression levels of antioxidase(SOD,GSH-Px,CAT)in MXC 32, 64mg groups were lower than that in control group. The activities of GSH, SOD and MDA and the mRNA expression levels of antioxidase were no significant difference between the 64mg MXC + Vit E 20 mg and the control group in ovary. Conclusion: MXC could increase the number of atresic follicle by disturbing the function of ovarian antioxidant system in female SD rats.The adverse effect was blocked by Vitamin E.