Transcapillary PO2gradients in contracting muscles across the fibre type and oxidative continuum
- 11 June 2020
- journal article
- research article
- Published by Wiley in Journal Of Physiology-London
- Vol. 598 (15), 3187-3202
- https://doi.org/10.1113/JP279608
Abstract
Key points Within skeletal muscle the greatest resistance to oxygen transport is thought to reside across the short distance at the red blood cell-myocyte interface. These structures generate a significant transmural oxygen pressure (PO2) gradient in mixed fibre-type muscle. Increasing O(2)flux across the capillary wall during exercise depends on: (i) the transmural O(2)pressure gradient, which is maintained in mixed-fibre muscle, and/or (ii) elevating diffusing properties between microvascular and interstitial compartments resulting, in part, from microvascular haemodynamics and red blood cell distribution. We evaluated the PO(2)within the microvascular and interstitial spaces of muscles spanning the slow- to fast-twitch fibre and high- to low-oxidative capacity spectrums, at rest and during contractions, to assess the magnitude of transcapillary PO(2)gradients in rats. Our findings demonstrate that, across the metabolic rest-contraction transition, the transcapillary pressure gradient for O(2)flux is: (i) maintained in all muscle types, and (ii) the lowest in contracting highly oxidative fast-twitch muscle. In mixed fibre-type skeletal muscle transcapillary PO(2)gradients (PO(2)mv-PO(2)is; microvascular and interstitial, respectively) drive O(2)flux across the blood-myocyte interface where the greatest resistance to that O(2)flux resides. We assessed a broad spectrum of fibre-type and oxidative-capacity rat muscles across the rest-to-contraction (1 Hz, 120 s) transient to test the novel hypotheses that: (i) slow-twitch PO(2)iswould be greater than fast-twitch, (ii) muscles with greater oxidative capacity have greater PO(2)isthan glycolytic counterparts, and (iii) whether PO(2)mv-PO(2)isat rest is maintained during contractions across all muscle types. PO(2)mvand PO(2)iswere determined via phosphorescence quenching in soleus (SOL; 91% type I+IIa fibres and CSa: similar to 21 mu mol min(-1)g(-1)), peroneal (PER; 33% and similar to 20 mu mol min(-1)g(-1)), mixed (MG; 9% and similar to 26 mu mol min(-1)g(-1)) and white gastrocnemius (WG; 0% and similar to 8 mu mol min(-1)g(-1)) across the rest-contraction transient. PO(2)mvwas higher than PO(2)isin each muscle (similar to 6-13 mmHg;P < 0.05). SOL PO(2)is(area)was greater than in the fast-twitch muscles during contractions (P < 0.05). Oxidative muscles had greater PO(2)is(nadir)(9.4 +/- 0.8, 7.4 +/- 0.9 and 6.4 +/- 0.4; SOL, PER and MG, respectively) than WG (3.0 +/- 0.3 mmHg,P < 0.05). The magnitude of PO(2)mv-PO(2)isat rest decreased during contractions in MG only (similar to 11 to 7 mmHg; time x (PO(2)mv-PO(2)is) interaction,P < 0.05). These data support the hypothesis that, since transcapillary PO(2)gradients during contractions are maintained in all muscle types, increased O(2)flux must occur via enhanced intracapillary diffusing conductance, which is most extreme in highly oxidative fast-twitch muscle.Funding Information
- National Institutes of Health (F31HL145981)
This publication has 89 references indexed in Scilit:
- Effects of nitrate supplementation via beetroot juice on contracting rat skeletal muscle microvascular oxygen pressure dynamicsRespiratory Physiology & Neurobiology, 2013
- Muscle oxygen transport and utilization in heart failure: implications for exercise (in)toleranceAmerican Journal of Physiology-Heart and Circulatory Physiology, 2012
- Two New “Protected” Oxyphors for Biological Oximetry: Properties and Application in Tumor ImagingAnalytical Chemistry, 2011
- Isolated Quadriceps Training Increases Maximal Exercise Capacity in Chronic Heart Failure: The Role of Skeletal Muscle Convective and Diffusive Oxygen TransportJournal of the American College of Cardiology, 2011
- Adrenergic control of vascular resistance varies in muscles composed of different fiber types: influence of the vascular endotheliumAmerican Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2011
- Critical speed in the rat: implications for hindlimb muscle blood flow distribution and fibre recruitmentJournal Of Physiology-London, 2010
- Myoglobin concentration in skeletal muscle fibers of chronic heart failure patientsJournal of Applied Physiology, 2009
- Phosphocreatine recovery kinetics following low- and high-intensity exercise in human triceps surae and rat posterior hindlimb musclesAmerican Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2009
- Oxygen Exchange Profile in Rat Muscles of Contrasting Fibre TypesJournal Of Physiology-London, 2003
- Diffusive resistance to O2 transport in muscleActa Physiologica Scandinavica, 2000