Martin Nicolas, Kraffe Edouard, Guderley Helga
Département de Biologie, Université Laval, Québec G1K7P4, Canada.
Comp Biochem Physiol A Mol Integr Physiol. 2009 Apr;152(4):599-603. doi: 10.1016/j.cbpa.2009.01.010.
In nature, seasons may be more reliably announced by changes in photoperiod than in temperature. To evaluate the role of day length in setting oxidative capacities of trout muscle mitochondria, we acclimated trout to summer (15 degrees C, 16L:8D), winter (5 degrees C, 8L:16D) and mixed conditions (15 degrees C, 8L:16D). Maximal oxidative capacities of isolated mitochondria at 5 and 15 degrees C were higher in mixed than summer conditions and higher again in winter conditions. At 5 degrees C, state 4 rates changed little with acclimation state whereas at 15 degrees C state 4 rates were lower in summer than in mixed or winter conditions. Using concentrations of the adenylate nucleotide translocase as the denominator for these rates gave much the same conclusions. By using inhibitors to block flux at specific points in the electron transport chain, we found that flux through Complexes II-IV was lowest in summer acclimated trout, increased upon acclimation to mixed and to winter conditions. Flux through complex IV was similar in trout acclimated to summer and mixed conditions, but increased significantly with acclimation to winter conditions. Flux through complex IV was 1.5 fold higher than state 3 rates for summer-acclimated trout but was similar to state 3 rates in trout acclimated to mixed or winter conditions. Our results indicate that a reduction in day length initiates increases in mitochondrial oxidative capacity typically associated with cold acclimation and that acclimation to both cold temperatures and short day lengths enhanced these changes. The overall similarity of the responses of state 3, of flux through complexes II-IV and of flux through complex IV suggests that a generalised mechanism such as changes in the phospholipid composition of the inner mitochondrial membrane may coordinate these changes.
在自然界中，季节变化或许通过光周期的改变比温度变化能更可靠地被预示。为了评估日照长度在设定虹鳟鱼肌肉线粒体氧化能力中的作用，我们将虹鳟鱼分别驯化于夏季（15摄氏度，16小时光照：8小时黑暗）、冬季（5摄氏度，8小时光照：16小时黑暗）以及混合条件（15摄氏度，8小时光照：16小时黑暗）下。在5摄氏度和15摄氏度时，分离出线粒体的最大氧化能力在混合条件下高于夏季条件，在冬季条件下又更高。在5摄氏度时，状态4速率随驯化状态变化不大，而在15摄氏度时，夏季的状态4速率低于混合或冬季条件。以腺苷酸转位酶的浓度作为这些速率的分母得出了大致相同的结论。通过使用抑制剂来阻断电子传递链中特定点的通量，我们发现，在夏季驯化的虹鳟鱼中，通过复合物II - IV的通量最低，在适应混合和冬季条件后增加。在适应夏季和混合条件的虹鳟鱼中，通过复合物IV的通量相似，但在适应冬季条件后显著增加。对于夏季驯化的虹鳟鱼，通过复合物IV的通量比状态3速率高1.5倍，但在适应混合或冬季条件的虹鳟鱼中与状态3速率相似。我们的结果表明，日照长度的缩短引发了通常与冷驯化相关的线粒体氧化能力的增加，并且对低温和短日照长度的适应增强了这些变化。状态3、通过复合物II - IV的通量以及通过复合物IV的通量的反应的总体相似性表明，一种普遍的机制，如线粒体内膜磷脂组成的变化，可能协调这些变化。
