Changes in serum triiodothyronine kinetics and hepatic type I 5'-deiodinase activity of cold-exposed swine.
Changes in serum triiodothyronine kinetics and hepatic type I 5'-deiodinase activity of cold-exposed swine.
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冷暴露猪血清三碘甲状腺原氨酸动力学和肝 I 型 5-脱碘酶活性的变化。
DOI：
10.1152/ajpendo.1994.266.5.e786
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
B. Young
中科院分区：
文献类型：
--
作者：
H. Reed;M. Quesada;R. Hesslink;M. D'Alesandro;M. Hays;R. Christopherson;B. V. Turner;B. Young
暴露于冷空气的猪血清总三碘甲状腺原氨酸（TT 3）和游离T3（FT 3）值升高。为了表征这些增加的机制，我们通过使用多室（MC）和非室（NC）方法和体外肝I型碘甲腺原氨酸5 '-脱碘酶（5' D-I）活性测定了静脉推注125 I标记的T3后的体内动力学参数。将10头5月龄公猪随机分为两组，在对照（22 ℃）或寒冷（4 ℃）条件下生活25天。冷暴露的动物比对照动物多消耗50%的卡路里，但在总体重、体脂百分比或血浆体积方面没有差异。与对照组相比，冷暴露组动物甲状腺重量增加86%（P < 0.004），血清总甲状腺素（TT 4）（48%）、游离T4（FT 4）（61%）、TT 3（103%）和FT 3（107%）也增加，而血清促甲状腺激素（TSH）无差异。当使用MC和NC技术时，两组之间的T3血浆清除率相似。然而，冷处理动物的T3血浆出现率（PAR）比对照组增加110%（P < 0.001），比NC方法增加83%（P < 0.001）。与对照组相比，T3组动物总激素池增加76%（MC）和53%（NC）（P < 0.01）。肝5 ′ D-I米氏常数各组间无差异，但最大酶速率增加（106%，P < 0.02）。因此，冷暴露25天与增加的能量摄入、甲状腺大小、T3 PAR和肝脏5 'D-I活性相关，而血清TSH变化不大。
Swine exposed to cold air have elevated serum values of total triiodothyronine (TT3) and free T3 (FT3). To characterize the mechanism of these increases, we measured in vivo kinetic parameters after a bolus intravenous injection of 125I-labeled T3 by use of both multicompartmental (MC) and noncompartmental (NC) methods and in vitro hepatic type I iodothyronine 5'-deiodinase (5'D-I) activity. Ten ad libitum-fed 5-mo-old boars were divided into two groups, living for 25 days in either control (22 degrees C) or cold (4 degrees C) conditions. Cold-exposed animals consumed 50% more calories than control animals but showed no difference in total body weight, percent body fat, or plasma volume. Thyroid gland weight was increased 86% (P < 0.004), as was serum total thyroxine (TT4) (48%), free T4 (FT4) (61%), TT3 (103%), and FT3 (107%), whereas serum thyrotropin (TSH) was not different in cold-exposed compared with control animals. The T3 plasma clearance rate was similar between groups when both MC and NC techniques were used. However, T3 plasma appearance rate (PAR) was elevated in cold-treated animals 110% over controls by MC (P < 0.001) and 83% by NC methods (P < 0.001). The animal total hormone pool of T3 was increased 76% (MC) and 53% (NC) compared with control (P < 0.01). The Michaelis constant of hepatic 5'D-I was not different between groups, but the maximum enzyme velocity increased (106%; P < 0.02). Therefore cold exposure for 25 days is associated with increased energy intake, thyroid size, T3 PAR, and hepatic 5'D-I activity with little change in serum TSH.