| Organic tin compounds are metallorganic compounds formed by tin and carbon. General formula:RnSnX4-n (n=1-4, R is alkyl or aryl) Orgnao-tin Compounds were wildly used as the catalyst, stabilizer, agricultural pesticides, fungicides and daily supplies coatings and mildew preventive. As widely used, Organic tin compounds have caused serious pollution on the global environment. Organic tin compounds can be absorbed through the respiratory tract, gastrointestinal tract, and skin. Tributyltin is an important kind of organic tin compounds, the existing research showed TBT has immune toxicity, neurotoxicity, reproductive toxicity on mammals,Objective:To explore the effects of low-dose TBT exposure during gestation and lactation of KM mice on the endocrine and reproductive system. And to explore the possible effects to the human offspring.Methods:1. Treatment of Laboratory AnimalThe clean healthy adult Pregnant KM mice were randomly divided into 4 groups,6 in each group, they were given doses of TBT (100,10,1,0μg/kg) by gavage from days 6 of gestation to the end of lactation. Cross-breed F1 generation of offspring within the same dose group.after feeding 90 days, Weaned on postnatal day 21.2.Testing and observation of animal behaviour Accounting the number of offspring, male and female number, body weight of the newborn when the mice were born, checking the abnormality and death number. Weighing the body weight of the offspring on postnatal day(PND) 1,3,5,7,14,21. Examining the eye opening on PND12, the vagina opening on PND20 and the foreskin separate on PND28. weighing the body weight each week after ablactation and calculate the net increase of body weight each muose. Measuring the Righting Reflex and Cliff-drop Aversion Reflex on PNDs 3,5,7,9,14. Observing the hearing shock reflection, and record the day of positive reflection occurs when the shock of hearing days.3. Determination of biomarkersOn PND49,10 male and female offspring mice were randomly selected in each group and killed after weighed. The brain, thymus, testicle, epididymis or metra and ovary were weighed for account of viscera coefficient. Analysis sperm membrane integrity and sperm chromatin status of Fl generation by flow cytometry (FCM). Analysis the estrogen receptorα(ER-α) and estrogen receptorβ(ER-β) protein expression in female ovaries of estrogen receptorα(ER-α) and Estrogen receptorβ(ER-β) expression, and the aromatase protein in hypothalamus.Results:The effects of TBT exposure to pregnancy mice:Comparing to the control group, the pregnancy mice body weight gain was significantly lower in 10μg/kg and 100μg/kg group(P<0.01). There were no significantly differences in average litter number, mortality during lactation and the sex ratio between treatment groups and control group(P>0.05).1. Changes in animal behaviorComparing with the control group, the eye opening time were significantly delayed in treatment groups. The Cliff-Drop Aversion Reflex in PND7 of treatment groups and the 1μg/kg and 100μg/kg groups in PND3 and the righting reflex time of 10μg/kg and 100μg/kg groups were significantly delayed than the control group. The body weight of treatment groups in PNDs 3,5,21 and 10μg/kg group in PND1 were significantly lower than the control group. The weight gain of the 100μg/kg group during PND1-3 and the 10μg/kg and 100μg/kg groups during PND14-21 were significantly lower than the control group(P<0.05,P<0.01). There were no significantly difference in the Righting Reflex between the treatment groups and the control group(P>0.05).2. Changes in animal development index and biomarkersThe effects of TBT exposure to the reproductive system of female:Comparing with the control group, the vagina opening and menarche were significantly ahead in treatment groups, and the body weight when menarche of the offspring was significantly lower (P<0.01). the body weight of treatment group in PND21 was significantly lower than the control group, the body weight gain of 10μg/kg group during PND21-49 was significantly higher than the control group(P<0.01,P<0.05), The foreskin separation time of 10μg/kg dose group in F2 generation was significantly delayed than the control group; the weight on foreskin separation time of all dose group in F2 generation was not significantly delayed than the control group; the sperm count and sperm abnormality has no significant difference compared with the control group. Western blotting analysis showed that estrogen receptor (ER-a and ER-β) protein expression in testis and ovary are associated with elevated TBT gradually weakened, and have the dose-effect relationships, aromatase Protein expression in testis and ovary were also gradually weakened with the concentration of TBT, and have the dose-effect relationships.Conlusions:1.Exposure to low doses of TBT during pregnancy and lactation can produce maternal toxicity, so that reduced body weight gain of pregnant rats. It can affect the growth and development and the role of endocrine disruption in offspring, and can make the F1 generation of precocious puberty in female mice.2. Exposure to low doses of TBT during pregnancy and lactation can lead to early neurobehavioral retardation.3. Exposure to low doses of TBT during pregnancy and lactation have impact on spermatogenesis, sperm quality, epididymal sperm morphology and chromatin structure of the plasma membrane.4. Exposure to low doses of TBT during pregnancy and lactation have impact on the expression of the protein of estrogen receptor in the testis and ovary expression and the expression of the protein of aromatase in the brain, testis and ovary.5. According to this study, we consider that WHO under estimate the potential hazardous of TBT when they rule the tolerable daily intake of TBT. The mice were exposed to EDCs during peripartal, checking the time of vagina opening and menarche, this may be a simple, economy, easy progress and credibility method to assess the EDCs. |
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