[HTML][HTML] Hypothermia decreases O2 cost for ex vivo contraction in mouse skeletal muscle
Medicine and science in sports and exercise, 2018•ncbi.nlm.nih.gov
Methods Isolated mouse extensor digitorum longus (EDL) muscles were incubated in a
temperature-controlled (37 C or 25 C) bath that included an O 2 probe. EDL muscles from
one limb were subjected to the measurement of resting mVO 2, and the contralateral EDL
muscles were used for the measurement of mVO 2 with electrically-stimulated contraction.
For the resting protocol, muscles were suspended at resting tension for 15 mins with
continuous O 2 recordings. For the contraction protocol, EDL muscles underwent ten …
temperature-controlled (37 C or 25 C) bath that included an O 2 probe. EDL muscles from
one limb were subjected to the measurement of resting mVO 2, and the contralateral EDL
muscles were used for the measurement of mVO 2 with electrically-stimulated contraction.
For the resting protocol, muscles were suspended at resting tension for 15 mins with
continuous O 2 recordings. For the contraction protocol, EDL muscles underwent ten …
Methods
Isolated mouse extensor digitorum longus (EDL) muscles were incubated in a temperature-controlled (37 C or 25 C) bath that included an O 2 probe. EDL muscles from one limb were subjected to the measurement of resting mVO 2, and the contralateral EDL muscles were used for the measurement of mVO 2 with electrically-stimulated contraction. For the resting protocol, muscles were suspended at resting tension for 15 mins with continuous O 2 recordings. For the contraction protocol, EDL muscles underwent ten electrically-stimulated isometric contractions with continuous O 2 recordings for 15 mins. The rate of O 2 disappearance was quantified as μmole O 2 per minute and normalized to the wet weight of the muscle.
Results
Resting mVO 2 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 mVO 2 at both 37 C and 25 C, which was sustained for~ 3 min post-contraction. During that period, mVO 2 was elevated~ 5-fold at both 37 C and 25 C. Greater contraction-induced mVO 2 at 37 C compared to 25 C occurred despite lower force generated at 37 C than at 25 C.
Conclusion
Together, O 2 cost for muscle contraction (force-time integral per O 2 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 O 2 than at 37 C.
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