Effect of different levels of iodine nutrition on secretion of placental hormone in pregnant rats / 中国地方病学杂志

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 weightslow 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.