Effects of different levels of iodine concentration on insulin-like growth factors Ⅰ mRNA expression of thyroid and breast in lactating rats

Objective To study the effects of different levels of iodine concentration on insulin-like growth factors Ⅰ (IGF-1) mRNA expression of thyroid and breast in lactating rats. Methods Thirty Wistar female rats, having been weaned for 1 month, were randomly divided into three groups according to their body weights, i. e. :low iodine(LI) group,adequate iodine(AI) group, high iodine(HI) group, 10 rats in each group. Synthetic fodder and deionized water containing iodine of 0,150,3000 μg/L was respectively fed to these rats. After fed for 3 months, the rats mated and had offspring. Their mammary glands, thyroids and serum were sampled at lactation day 5. The serum iodine of lactating rats were determined by moderate acid digestion method, level of T3 and T4 were determined by radioimmunoassay method, and the expressions of IGF-1 mRNA of mammary glands and thyroids were determined by real-time fluorescence quantitative PCR assay. Results The value of serum iodine of LI group (17.38±3.27) μg/L] was lower than that of AI group (43.42±6.92) μg/L, P<0.05], and the value of serum iodine of HI group(350.10±38.46)μg/L] was higher than that of AI group (P<0.05). The level of T3 of LI group and HI group (1.11±0.25), (1.61±0.33)μg/L] reduced obviously compared with that of AI group(2.18±0.46) μg/L, P<0.05]. The mean of T4 of LI group and HI group(33.40±11.11),(56.54±10.38)μg/L] had no statistical significance compared with AI group(44.02±12.51)μg/L, P>0.05), but the level of T4 of LI group was lower than that of HI group(P<0.05). The level of IGF-1 mRNA expression of thyroid in LI group and HI group (0.34±0.08, 0.23±0.08) was higher than that of AI group(0.15±0.03, P<0.05). The level of IGF-1 mRNA expression of lactating mammary in LI group(0.59±0.18) was higher than that of AI group(0.40±0.10, P<0.05). The level of IGF-1 mRNA expression of thyroid was lower than that of breast between the same group(t=3.54, 6.44,2.62, all P<0.05). Conclusion Iodine could affect IGF-1 mRNA expression of thyroid and lactating mammary, and IGF-1 mRNA expression of lactating mammary was stronger than that of the thyroid.