ABSTRACT
Objective To observe the effect of different levels of iodine nutrition on rat maternal thyroid function during pregnancy.Methods A total of 225 Wistar rats one month after weaning were involved in the study(female 165,male 60,body mass 80 to 100 g).Female rats were randomly divided into six groups by body mass:control group(NI group),iodine deficiency 1 and 2 groups(LI1,LI2 groups),iodine excess 1 and 2 groups (HI1,HI2 groups),and the control of not pregnant group(NNI group).There were 30 rats in 1-5 groups and 15 rats in group 6.LI1,LI2 groups:low iodine diet + deionized water of no iodine or iodine-containing 5 μg/L; HI1,HI2 groups:normal diet + deionized water of iodine 3000,10 000 μg/L; NI,NNI groups:normal diet + deionized water of iodine-containing 50 μg/L.After 12 weeks,the females(except group 6) mated the male by 2 ∶ 1,and then each pregnant female rat was fed in a single cage.The female mice were sacrificed in the first(5 ± 2)d,the second (12 ± 2)d and the third trimesters of pregnancy (17 ± 2)d,respectively,and there blood samples and thyroid were obtained.Serum total thyroxine(TT4),free thyroxine(FT4),total triiodothyronine (TT3),free triiodothyronine (FT3) and thyroid stimulating hormone(TSH) were determined by radioimmunoassay and serum thyroglobulin(TG) and thyroid-binding globulin (TBG) were determined by enzyme-linked immunosorbent assay.Results ①Thyroid absolute quality and relative quality was compared among groups,and the differences were statistically significant (F =16.55,24.25,F ＜ 0.01 or ＜ 0.05).②At the first,the second and the third trimesters of pregnancy,the differences of maternal serum TT4 and FT4 between groups were statistically significant(F =5.02,13.41,17.39,41.89,23.72,48.64,P ＜ 0.01 or ＜ 0.05).Female rats in NI,HI1 and HI2 groups in different pregnant periods among inner groups were compared,and the differences of serum TT4 and FT4 were statistically significant(F=3.27,6.98,8.22,8.65,29.68,7.90,P ＜ 0.01 or ＜ 0.05).③ In the first and the third trimesters of pregnancy,maternal serum TT3 was compared among groups,and the differences were statistically significant(F=3.59,8.22,P ＜ 0.05 or ＜ 0.01) ; in the second and the third trimesters of pregnancy,maternal serum FT3 was compared among groups,and the difference was statistically significant(F =3.86,4.26,P ＜ 0.05 or ＜ 0.01).Female rats in NI,LI1 and HI1 groups in different pregnant periods among inner groups were compared,and the differences of maternal serum TT3 were statistically significant(F =8.77,7.11,6.28,P ＜ 0.01 or ＜ 0.05).④At the first,the second and the third trimesters of pregnancy,the differences of maternal serum TG and TBG were compared in groups,and the differences were statistically significant(F =5.47,3.62,9.35,4.15,13.16,22.78,P ＜ 0.01 or ＜ 0.05).The differences of maternal serum TG of HI1 group and of serum TBG of NI group in different pregnant periods among inner groups were statistically significant (F =3.18,7.94,P ＜ 0.05).⑤At the first,the second and the third trimesters of pregnancy,the differences of maternal serum TSH in groups were statistically significant(F =4.83,7.08,6.52,P ＜ 0.01); the differences of maternal serum TSH of all the 5 groups in different pregnant periods among inner groups were statistically significant (F =3.26,8.89,11.45,4.04,3.78,P ＜ 0.05).Conclusions Different levels of iodine nutrition can cause changes in thyroid function in rats maternal thyroid function during pregnancy; serum TT4,FT4 level decreases when iodine deficiency,and increase with iodine excess.Serum TT3,FT3 level of does not changed significantly due to compensatory regulation of the body.
ABSTRACT
ObjectiveTo study the mRNA expression of rat Insulin-like growth factors- Ⅰ (IGF- Ⅰ ) and Transforming growth factor-β1 (TGF-β1) in thyroid and placenta with different iodine intakes during pregnancy.MethodsOne hundred and fifty female Wistar rats,weighting 80 - 100 g,were randomly divided into five groups according to body weight,30 rats in each group.Each group was given deionized water containing different concentrations of iodine,50 μg/L(control group,NI),0 μg/L(iodine deficiency 1 group,LI1 ),5 μg/L(iodine deficiency 2 group,LI2),3000 μg/L(iodine excess 1 group,HI1 ),and 10 000 μg/L(iodine excess 2 group,HI2),respectively.After feeding for 12 weeks,the female rats were mated with male rats.The female rats were sacrificed at first(6,7 days),trimester( 12,13 days),and third trimesters( 19,20 days),respectively,then their thyroid and placenta were collected.The mRNA expressions of IGF- Ⅰ and TGF-1 in thyroid and placenta were detected by real-time quantitative PCR.Results①The actual thyroid weights of LI1 and LI2 groups[ (12.17 ± 5.41 ) × 10-2 g,(3.54 ± 1.21) × 10-2 g] were significantly higher than that of NI group[ (2.05 ± 0.50) × 10-2 g,all P ＜ 0.05] ;actual weights of HI1 and HI 2 groups[ (1.64 ± 0.27) × 10-2 g,(1.66 ± 0.29) × 10-2 g] were compared with that of NI group,the difference was not statistically significant(all P ＞ 0.05).②The mRNA expression of IGF- Ⅰ: at the first trimester,LI1 and LI2 groups(l.98 ± 0.35,1.47 ± 0.22) were all higher than that of NI group(1.01 ± 0.18,all P＜ 0.01 ),HI1 and HI2 groups(0.68 ± 0.16,0.75 ± 0.09) were lower than that of NI group(all P ＜ 0.01 );at the second trimester,HI2 group( 1.14 ± 0.17) was lower than that of NI group( 1.58 ± 0.33,P ＜ 0.01 ) ; at the third trimester,LI2 and HI2 groups(1.47 ± 0.20,1.45 ± 0.35) were lower than that of NI group(2.20 ± 0.37,all P＜0.01).The mRNA expression of IGF- I level in NI group at the first,second,and third trimesters(1.01 ±0.18,1.58 ±0.33,2.20 ± 0.37) was up regulated gradually,pairwise comparisons were statistically significant(all P ＜ 0,01 ).③The mRNA expression of TGF-β1: at the first trimester,LI1 group (1.37 ± 0.13) was higher than NI group (1.05 ±0.18,P ＜ 0.01 ),HI1 and HI2 groups(0.50 ± 0.09,0.44 ± 0.11) were lower than NI group(all P＜ 0.01); at the second trimester,LI1 and HI2 groups(1.39 ± 0.28,1.17 ± 0.12) were higher than NI group(0.63 ± 0.22,all P ＜0.01 ) ; at the third trimester,LI1 and LI2 groups ( 1.57 ± 0.30,1.23 ± 0.20) were higher than NI group ( 0.68 ± 0.17,all P＜ 0.01).TGF-β1 mRNA expressions of NI group at the second (0.63 ± 0.22) and third trimesters(0.68 ± 0.17) were lower than that of the first trimester (1.05 ± 0.18,all P ＜ 0.01).④ Rats' IGF-Ⅰ mRNA expression in placental: at the second trimester HI1 group,HI2 group( 1.48 ± 0.16,1.45 ± 0.25) were all higher than the NI group ( 1.00 ± 0.10,all P ＜ 0.01 ) ; at third trimester,HI1 group ( 1.75 ± 0.15 ) were higher than the NI group ( 1.54 ± 0.29,P＜ 0.05),HI2 group(l.94 ± 0.31) were higher than the NI group(P ＜ 0.01 ).IGF- Ⅰ mRNA expression in placental of NI group at the third trimester was higher than the second trimester(P＜ 0.01).⑤ Rats' TGF-β1 mRNA expression in the placenta: at the second trimester and the third trimester of pregnancy there were no significant difference between the five groups(all P ＞ 0.05) ; NI group at the third trimester(0.83 ± 0.16) was lower than the second trimester(0.98 ± 0.20,P ＜ 0.05).Conclusions During pregnancy,IGF- I mRNA expression increases in thyroid under the conditions of iodine deficiency,and this effect is particularly significant in the first trimester; at the same time,TGF-β1 mRNA expression is increased,and this inhibition becomes clear with the deepening of iodine deficiency.Under the condition of iodine excess,the functions of IGF- Ⅰ and TGF-β1 in thyroid above-mentioned were relatively weak.With the development of gestational period,promoting tissues growth and differentiation effect of placenta's IGF- Ⅰ was more significant gradually,but,inhibited effect of TGF-β1 was weaken.
ABSTRACT
Objective To study the effect of different levels of iodine nutrition on secretion of placental hormone in pregnant rats.Methods Two hundred and twenty five Wistar rats (165 female,60 male),weighing about 80 - 100 g were used in the study.Female rats were randomly divided into five groups according to their body weights:low iodine group Ⅰ(LⅠ),low iodine group Ⅱ (LⅡ),adequate iodine(control) group(Al),high iodine group Ⅰ ( HⅠ ),and high iodine group Ⅱ (H Ⅱ ),and 33 rats in each group.Animals in the low iodine groups were fed low-iodine diet,the iodine content was 13.46 μg/kg,in addition,these rats drank deionized water which containing potassium iodated,the dose was 0 and 5 μg/L,respectively.The rats of adequate and the two high iodine groups were fed normal diet,the iodine content was 22.00 μg/kg,they also drank deionized water,containing potassium iodated 50,3000,and 10000 μg/L,respectively.The rats mated after 3 months of feeding,and were respectively sacrificed at early pregnancy(5 ± 2)d,second trimester( 12 ± 2)d,and third trimester of pregnancy(17 ± 2)d,and then their serum was taken.Serum human chorionic gonadotropin(HCG),human chorionic thyrotropin(HCT),and progesterone were measured by enzyme-linked immunosorbent assay (ELISA).Results In the third trimester,the serum levels of rat HCG were significantly different between groups(F =4.16,P ＜ 0.05).The means of rats serum HCG of the two low iodine groups [ (16.08 ± 4.45),(17.43 ± 2.70)U/L] were significantly higher compared with that of AI group[ (13.68 ± 3.52)U/L] in the third trimester(all P ＜ 0.01 ).In the second and third trimester,the levels of rats serum HCT were significantly different between groups(F =3.59,3.40,all P ＜ 0.05).The means of rats serum HCT of HI group [(70.11 ± 10.97)μU/L] in the second trimester and HII group[(74.93 ± 13.22)μU/L] in the third trimester were higher than those of AI group[ (57.14 ± 12.56),(58.17 ± 8.54)μU/L] significantly(all P ＜ 0.01 ).There were statistical differences of the means of serum progesterone among trimester of pregnancy(F =4.06,4.43,all P ＜ 0.05).The level of serum progesterone of the third trimester[ ( 1462.80 ± 286.48 )pmoL/L] compared to those of the first[ (1929.93 ± 158.37) pmol/L] and the second trimester[ (1856.44 ± 542.08)pmol/L] was decreased significantly(all P ＜ 0.05) in LI group.In the control group,the level of serum progesterone of the second trimester [ (2046.45 ± 475.67)pmol/L ] was significantly higher than the first trimester[ (1714.39 ± 461.71 )pmol/L,P ＜ 0.05 ].Conclusions During pregnancy,placenta could promote HCG secretion under iodine-deficient conditions.In addition,the placenta increases the secretion of HCT under conditions of excess iodine.In the condition of severe iodine deficiency,the secretion of serum progesterone decreases,and further decreases with prolongation of pregnancy,but it is opposite to the change of HCG during pregnancy.This phenomenon could lead to harmful pregnant outcomes easily.