Mitochondrial dysfunction and oxidative damage have long been suggested as critically important mechanisms underlying the ageing process in animals. However, conflicting data exist on whether this involves increased production of mitochondrial reactive oxygen species (ROS) during ageing. We employed high‐resolution respirometry and fluorometry on flight muscle (pectoralis major) and liver mitochondria to simultaneously examine mitochondrial function and ROS (H₂O₂) release rates in young (3 months) and old (4 years) zebra finches (Taeniopygia guttata). Respiratory capacities for oxidative phosphorylation did not differ between the two age groups in either tissue. Respiratory control ratios (RCR) of liver mitochondria also did not differ between the age classes. However, RCR in muscle mitochondria was 55% lower in old relative to young birds, suggesting that muscle mitochondria in older individuals are less efficient. Interestingly, this observed reduction in muscle RCR was driven almost entirely by higher mitochondrial LEAK-state respiration. Maximum mitochondrial ROS release rates were found to be greater in both flight muscle (1.3-fold) and the liver (1.9-fold) of old birds. However, while maximum ROS (H₂O₂) release rates from mitochondria increased with age across both liver and muscle tissues, the liver demonstrated a proportionally greater age-related increase in ROS release than muscle. This difference in age-related increases in ROS release rates between muscle and liver tissues may be due to increased mitochondrial leakiness in the muscle, but not the liver, of older birds. This suggests that age-related changes in cellular function seem to occur in a tissue-specific manner in zebra finches, with flight muscle exhibiting signs of minimising age-related increase in ROS release, potentially to reduce damage to this crucial tissue in older individuals.

长期以来，线粒体功能障碍和氧化损伤一直被认为是动物衰老过程中至关重要的机制。然而，关于这是否涉及在衰老过程中线粒体活性氧 (ROS) 的产生增加，存在相互矛盾的数据。我们对飞行肌肉（胸大肌）和肝线粒体采用高分辨率呼​​吸测量法和荧光测量法，以同时检测年轻（3 个月）和年老（4 岁）斑胸草雀 ( Taeniopygia guttata ) 的线粒体功能和 ROS (H ₂ O ₂ ) 释放率). 氧化磷酸化的呼吸能力在任一组织中的两个年龄组之间没有差异。肝线粒体的呼吸控制比 (RCR) 在年龄组之间也没有差异。然而，肌肉线粒体中的 RCR 与幼鸟相比，年老鸟低 55%，这表明年长个体的肌肉线粒体效率较低。有趣的是，这种观察到的肌肉 RCR 的减少几乎完全是由更高的线粒体 LEAK 状态呼吸驱动的。在成年鸟类的飞行肌肉（1.3 倍）和肝脏（1.9 倍）中发现最大线粒体 ROS 释放率更高。然而，虽然最大 ROS (H ₂ O ₂) 线粒体在肝脏和肌肉组织中的释放率随着年龄的增长而增加，肝脏表现出与年龄相关的 ROS 释放比例高于肌肉。肌肉和肝脏组织之间与年龄相关的 ROS 释放率增加的差异可能是由于年长鸟类的肌肉而非肝脏中线粒体渗漏增加所致。这表明，与年龄相关的细胞功能变化似乎以组织特异性方式发生在斑胸草雀身上，飞行肌肉表现出最小化与年龄相关的 ROS 释放增加的迹象，可能会减少对老年人这一关键组织的损害。