树麻雀肝脏和肌肉产热特征的季节性变化

Seasonal changes in thermogenic properties of liver and muscle in tree sparrows Passer montanus

北温带的小型鸟类,通过增加产热来适应低温环境。基础代谢率(BMR)是内温动物能量预算的重要组成部分。本研究中我们分别在冬季和夏季测定了树麻雀(Passer montanus)的BMR、肝脏和肌肉的线粒体蛋白含量、线粒体呼吸及细胞色素C氧化酶(COX)活力及血清中甲状腺激素(T4)及甲状腺原氨酸(T3)含量的变化。结果显示:树麻雀的体重和BMR冬季显著高于夏季;肝脏的线粒体呼吸、肝脏和肌肉的COX活力冬季较高,夏季较低;血清T3浓度冬季明显高于夏季。这些结果表明:在野外条件下,肝脏和肌肉在细胞水平产热能力的提高和血清T3含量的增加,是树麻雀抵御冬季寒冷的重要方式之一。

Seasonal changes in avian physiology and behavior are considered to be a part of an adaptive strategy for survival, and basal metabolic rate （BMR） is important component of energy budget in endotherms. In order to understand seasonal changes in cellular and hormonal thermogenic properties in tree sparrows Passer montanas, we measured body mass and BMR, mitochondrial protein contents, mitochondrial state 4 respiration, cytochrome C oxidase （COX） activity in liver and muscle, as well as serum triiodothyronine （ T3 ） and thyroxine （ T4 ） concentration in the summer （ late June and July） and winter （ late December and January）. Oxygen consumption was measured using a closed-circuit respirometer, state 4 respiration in liver and muscle mitochondria was measured with a Clark electrode. Likewise, activities of COX of liver and muscle were measured using a Clark electrode. Both body mass and BMR were higher in winter than in summer, and serum T3 concentration was higher in winter than in summer. The mitochondrial state 4 respiration in liver, and COX activity in liver and muscle exhibited higher levels in winter and lower levels in summer. These data indicate that increase in thermogenic capacity at both organismal and cellular levels are important adjustments to cope with cold stress in wild tree sparrows