达乌尔黄鼠冷暴露、冬眠及激醒时的外周甲状腺激素水平变化

VARIATION OF PERIPHERAL THYROID HORMONE LEVEL IN DAURIAN GROUND SQUIRREL (SPERIMOPHILUS DAURICUS) DURING COLD EXPOSURE, HIBERNATION AND AROUSAL

探讨了达乌尔黄鼠在冷暴露、冬眠及激醒时的外周甲状腺激素水平变化和激素代谢。达乌尔黄鼠在非冬眠季节 ( 7～ 8月 )冷暴露 ( 4℃± 2℃ ) 1天 ,导致血清T3和T4浓度迅速增加 ,T3/T4不变 ;经 4周冷驯化后 ,T3维持在高水平上 ,T4降低 ,T3/T4增加 ,外周组织中的T4脱碘酶活性升高。表明冬眠动物与非冬眠动物的甲状腺机能及其激素代谢的冷适应性调节一致。在冬眠季 ( 12～ 1月 )的冬眠和激醒过程中 ,外周组织的T4脱碘酶活性、血清T3和T4水平比常温达乌尔黄鼠的高 ,显著高于夏季的水平 ,T3/T4不变。表明达乌尔黄鼠甲状腺机能及其激素水平存在季节性变化。

Wen investigated the variation of peripheral thyroid hormone level and the hormone metabolism in Daurian ground squirrel (Sperimophilus dauricus) during cold exposure, hibernation and arousal. S. dauricus was trapped at the outskirts of Yanggao County, Shanxi Province. The concentration of T 3 and T 4 in serum was determined by radioimmunoassay. Activity of type Ⅱ T 4 5′ deiodinase of brown adipose tissue (BAT) and liver was assayed by using a triiodothyronine RIA kit. A experiment of cold exposure was carried out between July to August (nonhibernation season). S. dauricus exposed to cold (4±2℃) for 1 day showed that the concentration of serum T 3 and T 4 increased quickly by 186% and 96%, respectively, and the ratio of T 3 to T 4 unchanged. The serum T 3 kept high level (2 6 fold of control) and T 4 decreased after cold exposure for 4 weeks. The activity of T 4 5′ deiodinase in BAT and liver rose significantly during cold, increasing by 460% and 230%, respectively, after 4 weeks cold exposure. It indicated that cold induced regulation of thyroid function and metabolism of thyroid hormone may be consistent between S. dauricus in nonhibernate season and nonhibernat rodent. Thyroid activity and the metabolism of thyroid hormones in peripheral tissues may be stimulated by different pathways. It led to increased T 4 utilization and elevated T 3 concentration in serum and local tissues, which may take part in the thermogenic regulation in animals exposed to cold. In hibernating S. dauricus from December to January, levels of serum T 3 and T 4 were 62% and 86% higher, respectively, than those in euthermic S. dauricus kept at 22℃ (nonbernation) as control; the activity of T 4 5′ deiodinase of BAT increased significantly, reached 296% of nonbernation. In arousing S. Dauricus, T 3 concentration more increased by 96% and 23%, compared with nonhiberation and hibernating. However, serum T 3/T 4 was not changed among the three groups. This may result from either decreased the turnover of thyroid hormones or the increased thyroid activity. The results demonstrated that there were seasonal changes of thyroid function and level of peripheral thyroid hormone in Daurian ground squirrel.