Hypothermia Decreases O2 Cost for Ex Vivo Contraction in Mouse Skeletal Muscle.
Hypothermia Decreases O2 Cost for Ex Vivo Contraction in Mouse Skeletal Muscle.
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DOI：
10.1249/mss.0000000000001673
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发表时间：
2018-10
影响因子：
4.1
通讯作者：
Funai K
中科院分区：
文献类型：
--
作者：
Ferrara PJ;Verkerke ARP;Brault JJ;Funai K
有证据表明，参与骨骼肌收缩活动的关键 ATP 酶的能量效率在低温条件下得到提高。然而，目前尚不清楚温度降低如何影响肌肉收缩引起的骨骼肌耗氧量（mVO2）。将离体的小鼠趾长伸肌 (EDL) 肌肉在包含 O2 探针的控温（37°C 或 25°C）浴中孵育。测量一侧肢体 EDL 肌肉的静息 mVO2，使用对侧 EDL 肌肉测量电刺激收缩时的 mVO2。对于静息方案，肌肉在静息张力下悬浮 15 分钟，并连续记录 O2。对于收缩方案，EDL 肌肉经历 10 次电刺激等长收缩，并持续记录 O2 15 分钟。 O2 消失的速率被量化为每分钟 μmol O2 并标准化为肌肉的湿重。 37°C 时的静息 mVO2 高于 25°C 时的静息 mVO2，这与较低温度会降低基础代谢率的观点一致。电刺激收缩在 37°C 和 25°C 下均显着增加 mVO2，并在收缩后持续约 3 分钟。在此期间，mVO2 在 37°C 和 25°C 下均升高约 5 倍。尽管 37°C 产生的力低于 25°C，但 37°C 时产生的收缩诱导 mVO2 高于 25°C。总之，肌肉收缩的 O2 成本（每消耗 O2 的力-时间积分）在 37°C 时比在 25°C 时更高。与 25°C 相比，37°C 时高能磷酸盐的水平与更高的能量需求一致。总之，这些结果表明，在低于正常温度下发生的肌肉收缩需要的氧气量比 37°C 时要少。
Evidence suggests that the energy efficiency of key ATPases involved in skeletal muscle contractile activity are improved in a hypothermic condition. However, it is unclear how a decrease in temperature affects skeletal muscle O2 consumption (mVO2) induced by muscle contraction. Isolated mouse extensor digitorum longus (EDL) muscles were incubated in a temperature-controlled (37°C or 25°C) bath that included an O2 probe. EDL muscles from one limb were subjected to the measurement of resting mVO2, and the contralateral EDL muscles were used for the measurement of mVO2 with electrically-stimulated contraction. For the resting protocol, muscles were suspended at resting tension for 15 mins with continuous O2 recordings. For the contraction protocol, EDL muscles underwent ten electrically-stimulated isometric contractions with continuous O2 recordings for 15 mins. The rate of O2 disappearance was quantified as μmole O2 per minute and normalized to the wet weight of the muscle. Resting mVO2 was greater at 37°C than at 25°C, consistent with the idea that lower temperature reduces basal metabolic rate. Electrically-stimulated contraction robustly increased mVO2 at both 37°C and 25°C, which was sustained for ~3 min post-contraction. During that period, mVO2 was elevated ~5-fold at both 37°C and 25°C. Greater contraction-induced mVO2 at 37°C compared to 25°C occurred despite lower force generated at 37°C than at 25°C. Together, O2 cost for muscle contraction (force-time integral per O2 consumed) was greater at 37°C than at 25°C. Levels of high-energy phosphates were consistent with greater energy demand at 37°C compared to 25°C. In conclusion, these results indicate that muscle contraction that occurs at subnormal temperature requires less O2 than at 37°C.