Wang Kun, Sun Yi-na, Liu Jia-yu, Yan Yu-qin, Chen Zu-pei
Institute of Endocrinology, Tianjin Medical University, Tianjin 300070, China.
Chin Med J (Engl). 2006 Nov 20;119(22):1899-903.
Type 1 deiodinase (D1) plays an important role in the metabolism of thyroid hormone and has close relationship with thyroid function. In this study we explore the effects of iodine intake on D1 activity and its mRNA expression and its possible mechanism.
Forty-eight Wistar rats were randomly divided into six groups with 8 in each: low iodine (LI), normal iodine (NI), five-fold iodine (HI(5)), ten-fold iodine (HI(10)), fifty-fold iodine (HI(50)), one hundred-fold iodine (HI(100)) group. Three months, six months and twelve months after admistration of potassium iodate, they were sacrificed and thyroids were excised. The expression of D1 mRNA in the thyroid tissue was determined by RT-PCR and D1 activity was analyzed by (125)I-rT3 as substrate. The thyroid hormone was measured with radioimmunoassay method.
Compared with NI group, D1 mRNA expression in LI groups slightly decreased, and D1 activity greatly increased. Both T(3) and T(4) in thyroid tissue significantly decreased, but the T(3)/T(4) ratio increased. D1 mRNA expression decreased in all HI groups, and D1 activity was significantly lower in HI groups. There was a tendency of decrease in D1 activity with increased doses of iodine intakes. There was no significant difference in T(4) in thyroid tissue between HI groups and NI group, but a tendency of decrease in T(3) level was found in all HI groups.
In the case of iodine deficiency, D1 activity increased greatly in order to convert more T(4) to T(3). Excess iodine can inhibit both D1 mRNA expression and its activity to protect organism from being injured by excessive T(3).
1型脱碘酶（D1）在甲状腺激素代谢中起重要作用，与甲状腺功能密切相关。本研究探讨碘摄入量对D1活性及其mRNA表达的影响及其可能机制。
48只Wistar大鼠随机分为6组，每组8只：低碘（LI）组、正常碘（NI）组、5倍碘（HI(5)）组、10倍碘（HI(10)）组、50倍碘（HI(50)）组、100倍碘（HI(100)）组。给予碘酸钾3个月、6个月和12个月后，将大鼠处死并切除甲状腺。采用RT-PCR法检测甲状腺组织中D1 mRNA的表达，以（125）I-rT3为底物分析D1活性。采用放射免疫分析法测定甲状腺激素。
与NI组相比，LI组D1 mRNA表达略有下降，而D1活性显著升高。甲状腺组织中T(3)和T(4)均显著降低，但T(3)/T(4)比值升高。所有HI组D1 mRNA表达均降低，HI组D1活性显著降低。随着碘摄入量增加，D1活性有降低趋势。HI组与NI组甲状腺组织中T(4)无显著差异，但所有HI组T(3)水平均有降低趋势。
在碘缺乏情况下，D1活性大幅升高，以将更多T(4)转化为T(3)。过量碘可抑制D1 mRNA表达及其活性，以保护机体免受过量T(3)的损伤。
