Transcapillary PO(2) gradients in contracting muscles across the fibre type and oxidative continuum.
Transcapillary PO(2) gradients in contracting muscles across the fibre type and oxidative continuum.
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DOI：
10.1113/jp279608
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发表时间：
2020-08
期刊：
影响因子：
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通讯作者：
Poole DC
中科院分区：
文献类型：
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作者：
Colburn TD;Hirai DM;Craig JC;Ferguson SK;Weber RE;Schulze KM;Behnke BJ;Musch TI;Poole DC
In mixed fibre type skeletal muscle transcapillary PO2 gradients (PO2mv−PO2is; microvascular and interstitial, respectively) drive O2 flux across the blood-myocyte interface where the greatest resistance to that O2 flux resides. Herein we assessed a broad spectrum of fibre type and oxidative capacity rat muscles across the rest-to-contractions (1 Hz, 120 s) transient to test the novel hypotheses that: i) slow-twitch PO2is would be greater than fast-twitch, ii) muscles with greater oxidative capacity have greater PO2is than glycolytic counterparts, and iii) whether PO2mv−PO2is at rest is maintained during contractions across all muscle types. PO2mv and PO2is were determined via phosphorescence quenching in soleus (SOL; 91% type I+IIa fibres and CSa: ~21 μmol min−1 g−1), peroneal (PER; 33% and ~20 μmol min−1 g−1), mixed (MG; 9% and ~26 μmol min−1 g−1) and white gastrocnemius (WG; 0% and ~8 μmol min−1 g−1) across the rest-contractions transient. PO2mv was higher than PO2is in each muscle (~6–13 mmHg; p<0.05). SOL PO2is area was greater than the fast-twitch muscles during contractions (p<0.05). Oxidative muscles had greater PO2is nadir (9.4 ± 0.8, 7.4 ± 0.9, and 6.4 ± 0.4; SOL, PER, MG respectively) than WG (3.0 ± 0.3 mmHg, p<0.05). The magnitude of PO2mv−PO2is at rest decreased during contractions in MG only (~11 to 7 mmHg; Time × (PO2mv−PO2is) Interaction, p<0.05). These data support that, since transcapillary PO2 gradients during contractions are maintained in all muscle types, increased O2 flux must occur via enhanced intracapillary diffusing conductance, which is most extreme in highly oxidative fast-twitch muscle.
