ABSTRACT
Objective To study the effects of different iodine intakes on rat iodine metabolism during pregnancy.Methods One hundred and fifty female Wistar rats (body weight 80-100 g) were randomly divided into five groups:control group(NI),lower iodine 1 and 2 groups(LI1 and LI2),High iodine 1 and 2 groups(HI1 and HI2) by weight,30 rats in each group.These rats were given deionized water containing different concentrations of iodine,50(NI),0 (LI1),5(LI2),3000(HI1) and 10000 μg/L(HI2),respectively.After 12 weeks,urine samples were collected before copulation.The rats were sacrificed at the first(6-7 days),second (12-13 days) and third trimesters(19-20 days),respectively,serum and amniotic fluid samples were collected.Urinary iodine and iodine level in the fetal amniotic fluid were measured by As3+-Ce4+ catalytic spectrophotometry.Serum iodine was measured by mild acid digestion method.Results The baseline medians of urinary iodine of LI1 and LI2 groups(5.96,15.92 μg/L) were significantly lower than that of the NI group(43.75 μg/L,all P ＜ 0.01),and the values of HI and HI2 groups(5263.96,20389.64 μg/L) were significantly higher than that of the NI group (all P ＜ 0.01).The median of urinary iodine during pregnancy was significantly lower than that of the baseline of no pregnancy(all P ＜ 0.01).The medians of urinary iodine of the NI group at the first and the second trimesters (28.97,34.34 μg/L) were significantly lower than that of the third trimester(42.31 μg/L,all P ＜ 0.01).The means of serum iodine of LI1 and LI2 groups[(3.68 ± 1.69),(10.45 ± 4.16) μg/L] were significantly lower than that of the NI group [(23.68 ± 3.85)μg/L,all P ＜ 0.05],and the means of serum iodine of HI1 and HT2 groups [(502.67 ± 97.03),(822.15 ± 139.45)μg/L] were significantly higher than that of the NI group (all P ＜ 0.01).Although the mean of serum iodine of HI group gradually decreased with the progression of gestation,the difference was not statistically significant(all P ＞ 0.05).The iodine levels in amniotic fluid of fetal rats at the second and the third trimesters in LI1 group(0.85,3.00 μg/L) were significantly lower than that of the NI group(3.56,7.91 μg/L,all P ＜ 0.01),but the difference was not statistically significant between the iodine level in amniotic fluid of fetal rats of the LI2 and the NI groups at the second and the third trimesters(all P ＞ 0.05).The iodine levels in amniotic fluid of fetal rats at the second and the third trimesters in the HI1 group(49.59,171.21 μg/L) were significantly higher than that of the NI group(all P ＜ 0.01).The iodine levels in amniotic fluid of fetal rats at the second and the third trimesters in HI2 group (98.76,544.77 μg/L) were significantly higher than that of the NI group(all P ＜ 0.01).The iodine level in amniotic fluid of fetal rats in the third trimester was significantly higher than that of the second trimester in all the groups (all P ＜ 0.01).The ratios of serum iodine and urinary iodine of the LI1 and the LI2 groups (1.29 ± 1.14,1.70 ± 1.01) were significantly higher than that of the NI group(0.51 ± 0.37,all P ＜0.01),and that of the HI1 and the HI2 groups(0.21 ± 0.07,0.11 ± 0.07) were significantly lower than that of the NI group (all P ＜ 0.01).The ratios of amniotic fluid iodine and serum iodine of the LI and the LI2 groups (0.19 ± 0.15,0.32 ± 0.17) were significantly higher than that of the NI group(0.13 ± 0.05,P ＜ 0.01),but the difference was not statistically significant between HI1 and HI2 groups(0.09 ± 0.03,0.11 ± 0.04) and NI group(all P ＞ 0.05).The ratio of amniotic fluid iodine and serum iodine of the third trimester was significantly higher than that of the second trimester(all P ＜ 0.05).Conclusions Different iodine intake leads to changes in the levels of maternal iodine metabolism in rats during pregnancy.There probably is a protection mechanism in the mother's body,which protects the mother and the fetal from injury by iodine excess or iodine deficiency.