Kühn E R, Delmotte N M, Darras V M
Gen Comp Endocrinol. 1983 Jun;50(3):383-94. doi: 10.1016/0016-6480(83)90260-5.
The presence and circadian rhythmicity of thyroid hormones was studied in plasma and the thyroid gland of male Rana ridibunda before and during hibernation. Hibernating January frogs do have a lower T3 and T4 content of their thyroid gland whereas plasma levels of T3 are maintained and of T4 increased compared to fed September or October frogs. It seems likely that the increased photoperiod in January will be responsible for this increased T4 secretion, since controlled laboratory experiments performed in December did not reveal any influence of low temperature on circulating T3 or T4 levels. Also feeding does not influence circulating levels and thyroid content of thyroid hormones in frogs kept at room temperature during the month of January. A circadian rhythmicity of T3 and T4 in the thyroid gland is present in fed October frogs and in non fed December frogs acclimated at 5 degrees C for 12 days with an acrophase for T3 at approximately 1500 h and for T4 at around 1900 h, whereas in plasma only T3 does have circadian variations (acrophase about midnight) but not T4. When December frogs are acclimated to room temperature for 12 days, frogs are active again, but do not eat and have a lower body weight than frogs hibernating at 5 degrees C. Their T3 content of the thyroid gland has disappeared, but T4 thyroid content and plasma levels of T3 and T4 are maintained. As in hibernating frogs, no circadian variations in T4 plasma concentrations are present whereas the circadian thyroid T4 rhythm disappears. At the same time a dampening in rhythmicity for plasma T3 as judged by the significantly lower amplitude occurs. It is concluded that the persistence of circulating levels of thyroid hormones and of a circadian cyclicity for T3 in plasma in non feeding hibernating frogs may reflect the special metabolic state e.g. availability of food reserves in these animals.
研究了雄性湖蛙在冬眠前后血浆和甲状腺中甲状腺激素的存在及昼夜节律性。1月份冬眠的湖蛙甲状腺中T3和T4含量较低，而与9月或10月进食的湖蛙相比，其血浆中T3水平保持不变，T4水平升高。1月份日照时间增加可能是T4分泌增加的原因，因为12月进行的对照实验室实验未发现低温对循环中T3或T4水平有任何影响。同样，在1月份室温饲养的湖蛙中，进食也不会影响甲状腺激素的循环水平和甲状腺含量。10月进食的湖蛙以及12月未进食、在5摄氏度下适应12天的湖蛙，其甲状腺中存在T3和T4的昼夜节律性，T3的峰值相位约在15:00，T4的峰值相位约在19:00，而血浆中只有T3有昼夜变化（峰值相位约在午夜），T4没有。当12月的湖蛙在室温下适应12天时，它们再次活跃，但不进食，体重比在5摄氏度下冬眠的湖蛙轻。它们甲状腺中的T3含量消失，但T4甲状腺含量以及T3和T4的血浆水平保持不变。与冬眠湖蛙一样，血浆中T4浓度没有昼夜变化，而甲状腺T4节律消失。与此同时，血浆T3的节律性减弱，表现为振幅显著降低。结论是，非进食冬眠湖蛙血浆中甲状腺激素循环水平的持续存在以及T3的昼夜周期性可能反映了这些动物特殊的代谢状态，例如食物储备的可用性。
