Influence of iodine on mRNA expression of iodide transporter, insulin-like growth factor I and transforming growth factor beta in thyroid and mammary glands of lactating rats

Objective To observe the influence of iodine on mRNA expression of iodide transporter (NIS),insulin-like growth factor Ⅰ (IGF- Ⅰ ) and transforming growth factor beta(TGF-β) in thyroid and mammary glands of lactating rats and to explore the role of NIS,IGF- Ⅰ and TGF-β mRNA in iodine uptake in thyroid and mammary glands of lactating rats.Methods One hundred and one Wistar rats(80 female and 21 male),weighting 8 - 100 g were selected.These female rats were randomly divided into five groups according to their body weight:control group(NI,normal feed,drank deionized water containing iodine 50 μg/L) ; low iodine group 1 and 2(LI-1,LI-2,low iodine feed,drank deionized water containing iodine 0 and 5 μg/L,respectively); high iodine group 1 and 2(HI-1,HI-2,normal feed,drank deionized water containing iodine 3000 and 10 000 μg/L,respectively),16 rats in each group.After feeding for 3 months,the female and male rates were mated 3:1.The female rats in each group were sacrificed at the fifth and tenth day after postpartum.Thyroid and mammary glands were taken.The mRNA levels of NIS,IGF- Ⅰ and TGF-β in thyroid and mammary glands of lactating rats were determined by real time quantitative PCR.Results The fifth days after postartum,NIS,IGF- Ⅰ and TGF-β mRNA expression levels of thyroid and lactating mammary glands were different between groups,and the differences were statistically significant ( NIS:F =631.46,64.91,all P ＜ 0.01 ; IGF- Ⅰ:F =11.45,6.56,all P ＜ 0.01 ; TGF-β:F =291.83,304.53,all P ＜ 0.01).Compared with control group [NIS:0.0066 ± 0.0023, (0.1481 ± 0.0711 ) × 10-2; IGF- Ⅰ:0.0419 ± 0.0062,0.0542 ± 0.0044; TGF-β:0.1416 ± 0.0277,0.1670 ± 0.0499],regardless of thyroid or mammary gland,the NIS,IGF- Ⅰ and TGF-β mRNA expression of LI-1 [NIS:0.0447 ± 0.0110,(0.3030 ± 0.1831) × 10-2;IGF- Ⅰ:0.0662 ± 0.0078,0.0902 ± 0.008; IGF- Ⅰ:0.5514 ± 0.0508,0.6942 ± 0.0367],LI-2[NIS:0.0317 ±0.0081,(0.3017 ± 0.1601) × 10-2; IGF-I:0.0645 ± 0.0054,0.0894 ± 0.0093; TGF-β:0.5292 ± 0.0332,0.6704 ± 0.0277 ] was significantly increased (all P ＜ 0.01 ); the NIS mRNA expression of HI-1 [0.0043 ± 0.0011,(0.1233 ± 0.0954) × 10-2],HI-2[0.0037 ± 0.0017,(0.1058 ± 0.0854) × 10-2] was decreased(all P ＜ 0.05),while the expression of IGF-Ⅰ mRNA [0.0521 ± 0.0910,0.0715 ± 0.0026; 0.0516 ± 0.0078,0.0697 ± 0.0038] and TGF-β mRNA [0.2087 ± 0.0425,0.2361 ± 0.0425; 0.1971 ± 0.0237,0.2257 ± 0.0752 ] was increased (all P ＜ 0.05 ).The tenth days after postpartum,the mRNA expression levels of NIS,IGF- Ⅰ and TGF-β of thyroid and lactating mammary gland in rats were different between groups,and the differences were statistically significant (NIS:F =103.55,116.32,all P ＜ 0.01; IGF-Ⅰ:F =67.67,11.98,all P ＜ 0.01; TGF-β:F =74.30,381.30,all P ＜0.01 ).Compared with the control group[NIS:0.0069 ± 0.0011,(0.1337 ± 0.0599) × 10-2; IGF-Ⅰ:0.0390 ±0.0071,0.0534 ± 0.0056; TGF-β:0.1351 ± 0.0336,0.1534 ± 0.0320],the mRNA expression levels of NIS,IGF- Ⅰ and TGF-β of LI-1 [ NIS:0.0432 ± 0.0165,(0.2962 ± 0.0985 ) × 10-2; IGF- Ⅰ:0.0643 ± 0.0088,0.0873 ± 0.0055 ; TGF-β:0.5042 ± 0.0912,0.6408 ± 0.0420],LI-2[NIS:0.0287 ± 0.0111,(0.2873 ± 0.0862) × 10-2; IGF- Ⅰ:0.0621 ± 0.0094,0.0862 ± 0.0038; TGF-β:0.4893 ± 0.0504,0.6372 ± 0.0389] were significantly increased(all P ＜ 0.01 ); the NIS mRNA levels of HI-1 [ 0.0042 ± 0.0029,(0.1006 ± 0.0909) × 10-2],HI-2[0.0035 ± 0.0020,(0.0890 ± 0.0119) × 10-2] were decreased(all P＜ 0.05),while the expression of IGF-Ⅰ mRNA[0.0516 ± 0.0078,0.0668 ± 0.0071; 0.0508 ± 0.0089,0.0621 ± 0.0064] and TGF-β mRNA[0.2007 ± 0.0546,0.2175 ± 0.0370;0.1959 ± 0.0393,0.2097 ± 0.0425] were increased(all P ＜ 0.05 ).In thyroid and mammary glands,the comparisons of NIS,IGF,TGF-β mRNA expression of the fifth and tenth day after postartum,between each group were not statistically significant(all P ＜ 0.05).Conclusions There are regulatory mechanisms of thyroid and mammary glands of lactating rats in response to low or high iodine conditions.In low iodine,the expressions of NIS,IGF- Ⅰ and TGF-β mRNA in thyroid and mammary glands increase and iodide uptake ability is enhanced to meet the body needs.In high iodine,the expression of NIS mRNA decreases in thyroid and mammary glands.Due to the reduced ability of iodine uptake,iodine intake is reduced,thereby reducing the hazards of high iodine in filial rats. Key words: Iodine; Lactating; Iodide transporter; Insulin-like growth factor Ⅰ; Transforming growth factor beta