中文摘要：

目的 研究四氯二苯并二恶英（tetraehlorodibenzo-p-dioxin,TCDD）诱导腭裂的机制并探讨叶酸是否能够拮抗小鼠由2,3,7,8-TCDD诱导的腭裂.方法 将大鼠合笼饲养,将受孕（gestation day,GD）后小鼠70只分3组[对照组（20只）、TCDD组（26只）、叶酸组（24只）],对照组胃饲芝麻油50 ml/kg,TCDD组胃饲TCDD 24 μg/kg诱导腭裂模型,叶酸组胃饲叶酸5 mg/kg＋TCDD 24 μg/kg.在GD12.5、13.5、14.5、15.5和16.5孕鼠处死.GD16.5胎鼠体视显微镜检查腭裂类型,GD12.5、13.5、14.5、15.5胎鼠常规染色和扫描电镜观察,同时检测TCDD相关的芳香烃受体（arylhydroearbon re-ceptor,AHR）及腭发育相关的转化生长因子（transforming growth factor,TGF）β3表达及细胞凋亡.结果 腭裂发生率TCDD组为70.2％ （73/104）,叶酸组为66.3％ （61/92）,对照组5.4％ （4/74）.纤毛消失时间：对照组GD15.5、TCDD组GD12.5、叶酸组GD14.5.分子生物学检测发现TGF-β3表达与AHR成负相关,并且干扰到腭中嵴细胞极性和正常凋亡程序.结论 胃饲孕鼠叶酸未能够拮抗由2,3,7,8-TCDD诱导的腭裂,同时在该模型中腭中嵴上皮细胞极性和凋亡程序受到影响,TGF-β3表达受到抑制干扰腭的融合.

英文摘要：

Objective In this study,folic acid（FA） was tested for antiteratogenic effects on Tetrachlorodibenzo-p-dioxin（TCDD）-induced cleft palate in fetal mice.Methods In the present study,pregnant mice were dosed with TCDD 24 μg/kg and with or without FA 5 mg/kg body weight on gestation day 10.Control group mice received sesame oil 50 ml/kg body weight on gestation day（GD）10.The mice were sacrificed on GD12.5,GD13.5,GD14.5,GD15.5 and GD16.5.From each pregnant mouse on GD16.5,embryos were obtained to examine under a dissecting microscope,and routine histology was performed for detection and classification of palatal clefts.The fetuses were prepared for histologic examination,scanning electron microscope and TdT-mediated X-dUTP nick and labeling（TUNEL）.On GD12.5,GD13.5,GD14.5 and GD15.5.Meanwhile,real-time（RT）-PCR was employed to detect the mRNA expression levels about arylhydrocarbon receptor（AHR） and transforming growth factor（TGF）β3 in this animal model.Results Total frequencies of clefts were 70.2% in TCDD group（group B） and 66.3% in TCDD ＋ FA group（group C） in relation to control fetuses（group A）.Filopodia disappeared completely at the medial edge epithelia surface on GD15.5（group A）,GD12.5（group B） and GD14.5（group C）.the RT-PCR results showed that TGF-β3 expression was down-regulated on GD13.5 and GD14.5 compared to the control.Conclusions It is found that folic acid has no protects agaist 2.3.7.8-TCDD-indued cleft palate in the experiment.Meanwhile,TCDD repressed the TGF-β3 expression during the palatal development.Anormal apoptosis was induced by 2,3,7,8-TCDD at the medial edge epithelia（MEE） during the early development stage.