The effect of different levels of iodine nutrition on rat maternal thyroid function during pregnancy / 中国地方病学杂志

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 masscontrol 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 groupslow iodine diet + deionized water of no iodine or iodine-containing 5 μg/L; HI1,HI2 groupsnormal diet + deionized water of iodine 3000,10 000 μg/L; NI,NNI groupsnormal 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.