Study On The Effects And Mechanism Of Prenatal DEHP Exposure On Thyroid In Offspring Rats

Objective:To explore the interference of prenatal DEHP exposure on the thyroid,the thyroid histomorphology and serum THs levels,the expression level of THs synthesis related Ttf-1,Tshr,Nis,Tpo,Tg genes in thyroid,the expression level of TTR in serum,and the expression level of THs metabolism related D1,Cyp2b1,Ugt1a1 gene in liver of offspring rats were detected.Methods:64 healthy pregnant SD rats were randomly assigned to 4 groups(16 in each group)and treated with corn oil and 2,10,50 mg/kg DEHP by gavage from G14 to G19.From Postnatal day 21(PND21),the pup were weaned and separated by sex and measured body weight once a week.From PND42,One male and one female rats(8 in each group)were randomly selected.Taken femoral artery blood and the cervical vertebra was dislocated and sacrificed then rapidly separated thyroid and liver tissue.One male and one female rats(8 in each group)were selected and fixed by 4% paraformaldehyde perfusion through the heart after intraperitoneal injection of 10% chloral hydrate anesthesia.The thyroid tissue was taken for paraffin embedding and sectioned 6μm thick.The remaining rats were fed to adulthood(PND70)and the experiment was repeated.Serum levels of T3,T4 and TSH were determined by Luminex technology.Serum TTR levels were detected by ELISA.Real-time fluorescence quantitative PCR was used to detect gene expression level.The paraffin sections of thyroid were treated with HE staining and the histological observation.Results:(1)There was statistically significant at PND21 to PND49 body weight among the treated groups.Compared with the control group,2,10 and 50 mg/kg groups was decreased at PND21.10 and 50 mg/kg groups was decreased PND28,PND35 and PND49.10 mg/kg groups was decreased at PND42(P<0.05).There was statistically significant PND21,PND49 and PND56 body weight among the treated groups.Compared with the control group,10 and 50 mg/kg groups was decreased PND21.2 and 10 mg/kg groups was increased PND49.2 mg/kg groups was increased PND56(P<0.05).(2)There was statistically significant the serum levels of T4,T3 and TSH in male adolescent rats among the treated groups.Compared with the control group,10 mg/kg groups the serum level of the T4 was increased.10 and 50 mg/kg groups the serum level of T3 was increased,the serum level of TSH was decreased.There was statistically significant the serum levels of TSH in male adult rats among the treated groups.Compared with the control group,10 and 50 mg/kg groups the serum level of TSH was increased.There was no statistically significant the serum levels of T4,T3 and TSH in female adolescent rats among the treated groups the same as results of serum T4 and TSH levels in female adult rats.The serum level of T3 in 2mg/kg group was significantly lower than control group(P<0.05).(3)Compared with the control group,the thyroid follicular epithelial cells were flattened in adolescent rats,the follicular cavity diameter increased and the cell activity decreased.In adult rats,the thyroid follicular epithelial cells proliferated and arranged in disorder,and the follicular cavity diameter decreased.(4)There was statistically significant the expression of Ttf-1,Nis,Tpo and Tg genes in male adolescent rats among the treated groups.Compared with the control group,the expression level of Tpo genes in 50 mg/kg group was down-regulated,Ttf-1,Nis and Tg genes in 10 and 50mg/kg groups were down-regulated(P<0.05).There was statistically significant the expression of Ttf-1,Nis,Tpo genes in male adult rats among the treated groups.Compared with the control group,the expression levels of Nis genes in 10 mg/kg group were down-regulated,Tpo gene in 50 mg/kg group was down-regulated,Ttf-1 gene in 10,50mg/kg group was down-regulated(P<0.05).There was statistically significant the expression of Ttf-1,Nis,Tpo,Tg genes in female adolescent rats among the treated groups.Compared with the control group,the expression levels of four genes in the 10 and 50 mg/kg groups were down-regulated(P<0.05).There was statistically significant the expression of Ttf-1,Nis,Tpo genes in female adult rats among the treated groups.Compared with the control group,the expression level of Ttf-1 gene in the 10 and 50 mg/kg groups was down-regulated,Nis gene in the 2,10,50 mg/kg groups was down-regulated,Tpo gene in the 50 mg/kg groups was down-regulated(P<0.05).(5)There was statistically significant the serum levels of TTR protein in female adult rats among the treated groups(P<0.05).(6)There was statistically significant the expression of D1 and Ugt1a1 genes in male adolescent rats among the treated groups.Compared with the control group,the expression levels of genes in the 10 and 50 mg/kg groups were down-regulated(P<0.05).There was statistically significant the expression of D1 genes in male adult rats among the treated groups.Compared with the control group,the expression levels of genes in 50 mg/kg groups were down-regulated(P<0.05).There was statistically significant the expression of D1 and Ugt1a1 genes in female adolescent rats among the treated groups.Compared with the control group,the expression levels of D1 genes in the 10 and 50 mg/kg groups were down-regulated,Ugt1a1 genes in the 50 mg/kg groups were down-regulated(P<0.05).There was no statistically significant the expression of genes in female adult rats among the treated groups.Conclusion:(1)Prenatal DEHP exposure may interference thyroid tissue structure and function in offspring rats.(2)Prenatal DEHP exposure may interference the expression level of THs synthesis related Ttf-1,Tshr,Nis,Tpo,Tg genes in thyroid.(3)Interference the expression level of TTR in serum.(4)Interference the expression level of THs metabolism related D1,Cyp2b1,Ugt1a1 gene in liver.(5)Prenatal DEHP exposure may have different effects on rats at different physiological stages and different genders.