EFFECT OF HEAT EXPOSURE ON THE DIURNAL CHANGE OF BODY TEMPERATURE

在连续10天的黑暗阶段的后半部分期间将大鼠暴露于热负荷约5小时后，大鼠的体温在对应于先前热暴露时间的时间段内显著降低（Shido等人，1991年）。该项目的目的是阐明体温特征性下降的机制。热暴露（HE）大鼠在黑暗期的后半部分经受33.0 ℃约5 h，持续2周以上，对照（CN）大鼠保持在24 ℃。完成后的时间表，水平下丘脑温度（Thy），热损失，产热，摄食活动（FA）和身体运动的显着低于在CN期间，HE大鼠已暴露于热。即使在实验开始前6 h开始的禁食状态下，Thy仍存在显著差异。这些结果表明，Thy的特征性下降部分是由FA的减少介导的，然而，还有另一个因素。为了研究甲状腺激素和能量底物的血浆水平的贡献，在0000和1800 h之间的3 h间隔（暗相，0300-1500 h）测量三碘甲状腺原氨酸（T3）、游离T3（FT 3）、甲状腺素（T4）、游离T4（FT 4）、甘油三酯、非酯化脂肪酸、总蛋白和葡萄糖的血浆水平。血浆T3和FT 3水平在以前的热暴露期间显着高于在CN中的HE。在T4和FT 4水平中观察到类似的差异。两组之间的能量底物血浆水平没有差异。这些结果表明甲状腺激素对HE大鼠Thy特征性福尔斯下降的贡献最小。进一步的研究需要澄清的特点下降在你的机制。

After the rats were exposed to heat loaded for about 5 h during the last half of the dark phase for 10 consecutive days, body temperature of the rats significantly decreased during the period corresponding to that of the previous heat exposure time (Shido et al., 1991). The objective of this project was to clarify the mechanism of characteristic fall in body temperature. The heat-exposed (HE) rats were subjected to 33.0ﾟC for about 5 h in the last half of the dark phase for more than 2 weeks and control (CN) rats were kept at 24ﾟC. After the completion of the schedule, the levels of hypothalamic temperature (Thy), heat loss, heat production, feeding activity (FA) and body movement were significantly lower in the HE than in the CN during the period when the HE rats had been exposed to heat. Even in fasting condition from 6 h before the start of the experiment, significant difference in Thy still existed. These results suggest that the characteristic fall in Thy is partly mediated by the decrease in FA, however, there are also another contributors. To investigate the contribution of plasma levels of thyroid hormones and energy substrates, plasma levels of triiodothyronine (T3), free T3 (FT3), thyroxin (T4), free T4 (FT4), triglyceride, non esterified fatty acid, total protein and glucose were measured at 3 h interval between 0000 and 1800 h (dark phase, 0300-1500 h). Plasma levels of T3 and FT3 during the previous heat exposure period were significantly higher in the HE than in the CN. Similar differences were observed in T4 and FT4 levels. Plasma levels of energy substrates did not differ between 2 groups. These results suggest minimum contributions of thyroid hormones to the characteristic falls in Thy in the HE rats. Farther studies are required to clarify the mechanisms of the characteristic fall in Thy.