Impact of low iodine on thyroid structure and iodine uptake function in parental and second filial generation rats / 中华地方病学杂志

ABSTRACT

Objective To observe the effect of long-term intake of low iodine diet on thyroid morphological structure and sodium iodine transporter (NIS) in parental and second filial generation rats, and to explore the changes of NIS protein expression in iodine deficiency disease (IDD), so as to further verify and explore the mechanism of IDD. Methods Referring to "Nutritional Composition of Experimental Animals With Feed" (GB 14924.3-2010), the crops widely planted and with high edible rate in the traditional cretinism epidemic area of Xinjiang were used as the main feed components to prepare different levels of iodine (low iodine groups 1 and 2 feed the iodine contents were about 50 and 20 μg/kg). The IDD rat model was established by the three-generation two-nest method, that is, 132 SPF Wistar rats were selected after weaning, half males and half females, randomly divided into 3 groups according to body mass by random number table method: control group (N, 52 rats, 22 females, 30 males, the iodine content was about 300 μg/kg), low iodine groups 1 and 2 (LⅠ, LⅡ, 40 rats, 22 females, 18 males in each group). Twelve rats in each group were sacrificed at the end of 3, 6, 9 months, respectively, half males and half females. The relative weight of thyroid was calculated and the gross structure and microscopic pathology were observed. The expression of NIS protein was determined by Western blotting. At the end of 3 months after feeding, four female rats in each group were selected to mate with male rats in group N in 1 1, and the newborn mice were fed the same way for three months and then subcultured again. The rat generation continued to be fed according to the mother group, and 10-12 rats were sacrificed at the end of 3, 6, 9 months, respectively, and the specimens and observation indexes results were collected same as the parental rats. Results The relative weight of the thyroid in parental LⅠand LⅡ groups were higher than those in the N group at 6 and 9 months [female(19.67 ± 5.60), (23.81 ± 4.08) vs (10.14 ± 1.20);(22.24 ± 2.06), (33.51 ± 3.24) vs (9.80 ± 1.96);male(13.0 ± 3.70), (13.84 ± 4.08) vs (5.90 ± 1.20);(14.20 ± 2.67), (19.98 ± 2.84) vs (6.06 ± 0.76), P < 0.05], the females were higher than the males at 3, 6, 9 months (P<0.05). The relative weight of the thyroid in second filial generation LⅠand LⅡgroups were higher than that in the N group at 3, 6 and 9 months (P < 0.05). Except the 6 month LⅠ group, the relative weight of thyroid in the other groups was higher than that in the male (P<0.05). In prolonged iodine-deficiency process, LⅠ and LⅡ groups, the color of the thyroid gland for parental and second filial generation rats appeared darkening, hyperemia and swelling. At the same time, microscopic pathology showed that the thyroid gland of different generations showed increased follicles and smaller follicular cavities. Epithelial cell hyperplasia and interstitial fibrosis and interstitial inflammatory cell infiltration at the end of 9 months were observed. At 3, 6, and 9 months after low iodine, the expression of NIS protein in the LⅠ and LⅡ parental and second filial generation rats was higher than that in the N group (P<0.05). Conclusions Long-term low iodine in different levels of feed can cause compensatory thyroid enlargement and hyperplasia in both parental and offspring rats, the expression of NIS protein has continued to rise.