Intracellular oxygen tension limits muscle contraction‐induced change in muscle oxygen consumption under hypoxic conditions during Hb‐free perfusion

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• 作者：Hisashi Takakura ; Minoru Ojino ; Thomas Jue ; Tatsuya Yamada ; Yasuro Furuichi ; Takeshi Hashimoto ; Satoshi Iwase ; Kazumi Masuda
• 刊名：Physiological Reports
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：5
• 期：2
• 全文大小：583.4KB
• ISSN：2051-817X

文摘

Under acute hypoxic conditions, the muscle oxygen uptake (mpan data-equation-construct="true" class="math-equation-construct">pan data-equation-image="true" class="math-equation-image">pan>pan data-equation-mathml="true" class="math-equation-mathml" style="display:none">V˙pan>pan>O₂) during exercise is reduced by the restriction in oxygen-supplied volume to the mitochondria within the peripheral tissue. This suggests the existence of a factor restricting the mpan data-equation-construct="true" class="math-equation-construct">pan data-equation-image="true" class="math-equation-image">pan>pan data-equation-mathml="true" class="math-equation-mathml" style="display:none">V˙pan>pan>O₂ under hypoxic conditions at the peripheral tissue level. Therefore, this study set out to test the hypothesis that the restriction in mpan data-equation-construct="true" class="math-equation-construct">pan data-equation-image="true" class="math-equation-image">pan>pan data-equation-mathml="true" class="math-equation-mathml" style="display:none">V˙pan>pan>O₂ is regulated by the net decrease in intracellular oxygen tension equilibrated with myoglobin oxygen saturation (∆P_mbO₂) during muscle contraction under hypoxic conditions. The hindlimb of male Wistar rats (8 weeks old, n = 5) was perfused with hemoglobin-free Krebs–Henseleit buffer equilibrated with three different fractions of O₂ gas: 95.0%O₂, 71.3%O₂, and 47.5%O₂. The deoxygenated myoglobin (Mb) kinetics during muscle contraction were measured under each oxygen condition with a near-infrared spectroscopy. The ∆[deoxy-Mb] kinetics were converted to oxygen saturation of myoglobin (S_mbO₂), and the P_mbO₂ was then calculated based on the S_mbO₂ and the O₂ dissociation curve of the Mb. The S_mbO₂ and P_mbO₂ at rest decreased with the decrease in O₂ supply, and the muscle contraction caused a further decrease in S_mbO₂ and P_mbO₂ under all O₂ conditions. The net increase in mpan data-equation-construct="true" class="math-equation-construct">pan data-equation-image="true" class="math-equation-image">pan>pan data-equation-mathml="true" class="math-equation-mathml" style="display:none">V˙pan>pan>O₂ from the muscle contraction (∆mpan data-equation-construct="true" class="math-equation-construct">pan data-equation-image="true" class="math-equation-image">pan>pan data-equation-mathml="true" class="math-equation-mathml" style="display:none">V˙pan>pan>O₂) gradually decreased as the ∆P_mbO₂ decreased during muscle contraction. The results of this study suggest that ΔP_mbO₂ is a key determinant of the Δmpan data-equation-construct="true" class="math-equation-construct">pan data-equation-image="true" class="math-equation-image">pan>pan data-equation-mathml="true" class="math-equation-mathml" style="display:none">V˙pan>pan>O₂.