Laboratório de Biologia do Exercício, Departamento de Educação Física, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
Laboratório de Hemodinâmica da Atividade Locomotora, Escola de Educação Física e Esporte, Universidade de São Paulo, São Paulo, SP, Brazil; Escola de Artes, Ciências e Humanidades, Universidade de São Paulo, São Paulo, SP, Brazil.
J Therm Biol. 2021 Apr;97:102807. doi: 10.1016/j.jtherbio.2020.102807. Epub 2021 Feb 23.
The purpose of this study was to evaluate the circadian rhythm of core temperature (T) across aging in Spontaneously Hypertensive Rats (SHR) with comparison to the two rat strains often used as their normotensive control animals, namely, Wistar (WIS) and Wistar Kyoto (WKY).
WIS, WKY and SHR rats were subdivided into three different groups according their age: WIS16, WIS48, WIS72, WKY16, WKY48, WKY72, SHR16, SHR48 and SHR72 weeks-old. Body mass and blood pressure were periodically measured along the experiments. All animal group had their circadian rhythm of T evaluated over three consecutive days (72 h) by telemetry using an implanted temperature sensor. The T circadian rhythm was averaged in 1-h blocks and analyzed using the cosinor method.
Sixteen-week-old SHR (SHR16) presented higher T than WIS16 (from 06am to 06pm) and WKY16 (from 07am to 06pm). Both normotensive groups exhibited increases in T during circadian rhythm with aging. The cosinor analysis showed no differences between strains and ages for the acrophase. An age effect on the SHR strain (SHR16 < SHR72) was observed regarding the amplitude. SHR16 had higher values regarding MESOR compared to WIS16 and WKY16. In addition, WIS72 and WKY72 showed higher values than WIS16 and WKY16, respectively. Finally, no differences were observed in the strength rhythm analysis.
SHR presented impaired thermoregulatory control at only 16 weeks of age when showing a higher body temperature during the activity phase, while other circadian rhythm parameters showed no differences across aging. Therefore, in taking our results as a whole we can conclude that WIS and WKY are appropriate Wistar strains to be used as normotensive controls for SHR.
本研究旨在评估核心体温（T）随衰老在自发性高血压大鼠（SHR）中的昼夜节律，并与作为其正常血压对照动物的两种大鼠品系（Wistar [WIS] 和 Wistar Kyoto [WKY]）进行比较。
根据年龄将 WIS、WKY 和 SHR 大鼠分为三组：16 周龄、48 周龄和 72 周龄 WIS 组、16 周龄、48 周龄和 72 周龄 WKY 组、16 周龄、48 周龄和 72 周龄 SHR 组。实验过程中定期测量体重和血压。通过植入式温度传感器，使用遥测技术对所有动物组连续三天（72 小时）的 T 昼夜节律进行评估。T 昼夜节律以 1 小时为单位平均，并使用余弦法进行分析。
16 周龄 SHR（SHR16）的 T 高于 16 周龄 WIS（从早上 6 点到下午 6 点）和 16 周龄 WKY（从早上 7 点到下午 6 点）。两个正常血压组随年龄增长在昼夜节律中 T 升高。在相位方面，品系和年龄之间没有差异。在振幅方面，SHR 品系（SHR16<SHR72）存在年龄效应。与 WIS16 和 WKY16 相比，SHR16 的 MESOR 值更高。此外，与 WIS16 和 WKY16 相比，WIS72 和 WKY72 分别显示出更高的值。最后，在强度节律分析中没有观察到差异。
SHR 在仅 16 周龄时表现出受损的体温调节控制，在活动期表现出更高的体温，而其他昼夜节律参数在整个衰老过程中没有差异。因此，综合我们的结果可以得出结论，WIS 和 WKY 是合适的 Wistar 品系，可以作为 SHR 的正常血压对照。
