Males and females of many species, including humans, exhibit different muscle responses and adaptations to exercise stress; however, the molecular mechanisms that underlie these changes are poorly understood. Therefore, the present study assessed sex-related differences in intracellular signaling pathway responses to bouts of horizontal or downhill running in rat soleus muscles. Age-matched male and female Wistar rats (10 weeks old, n = 18/group) were either rested (control group) or subjected to an either a bout of horizontal (22 m/min, 20 min, 0° incline) or downhill (16 m/min, 10 min, − 16% incline) treadmill running. Soleus muscle samples were collected both prior to and immediately after exercise (n = 6/group). Intramuscular signaling responses to each type of exercise were determined via real-time (RT) PCR and western blot analyses. Although mTOR signaling (mTOR/S6K1/S6) responses to both horizontal and downhill exercise were found to be similar in both sexes, ERK phosphorylation levels were found to be significantly higher in male than in female rats after downhill exercise. Similarly, heat shock protein (Hsp) 72 and myostatin protein expression levels were both found to be significantly altered after downhill exercise: Hsp levels increased in male and decreased in female rats, whereas myostatin increased in female but decreased in male rats. Thus, the results of the present study suggest that downhill exercise may elicit sex-specific differential changes to Hsp72 expression, ERK phosphorylation, and myostatin-signaling activation in female compared with those in male rat soleus muscles. Further study is required to confirm these findings and to determine the way in which they impact sex-specific differences in exercise-induced muscle adaptations.

中文翻译：

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大鼠比目鱼肌信号传导途径对水平和下坡跑步的反应中的性别差异。

包括人类在内的许多物种的雄性和雌性表现出不同的肌肉反应和适应运动压力的能力；然而，对这些变化的分子机制了解甚少。因此，本研究评估了大鼠比目鱼肌水平或下坡跑步时细胞内信号通路反应的性别相关差异。年龄相匹配的雄性和雌性Wistar大鼠（10周大，n = 18 /组）被休息（对照组）或水平（22 m / min，20 min，0°倾斜）或下坡运动（16 m / min，10 min，-16％倾斜）跑步机。运动前和运动后立即采集比目鱼肌样本（n= 6 /组）。通过实时（RT）PCR和Western blot分析确定对每种运动的肌内信号传导反应。尽管发现男女在水平运动和下坡运动中对mTOR信号的响应（mTOR / S6K1 / S6）相似，但在下坡运动后，雄性大鼠的ERK磷酸化水平明显高于雌性大鼠。同样，在下坡运动后，热休克蛋白（Hsp）72和肌生长抑制素蛋白的表达水平也均发生了显着变化：雄性大鼠的Hsp水平升高，雌性大鼠的Hsp水平升高，而雌性大鼠的Myostatin升高，而雄性大鼠则降低。因此，本研究的结果表明，进行下坡运动可能会引起Hsp72表达，ERK磷酸化，与雄性大鼠比目鱼肌相比，雌性大鼠的肌生长抑制素和肌生长抑制素信号激活。需要进一步的研究来证实这些发现，并确定它们如何影响运动引起的肌肉适应中的性别差异。