Human skeletal muscle intracellular oxygenation: the impact of ambient oxygen availability

• Published in: The Journal of physiology 2006-03, Vol.571 (2), p.415-424
• Main Authors: Richardson, Russell S., Duteil, Sandrine, Wary, Claire, Wray, D. Walter, Hoff, Jan, Carlier, Pierre G.
• Format: Article
• Language: English
• Subjects: Adult; Blood Pressure - physiology; Cell Hypoxia - physiology; Cell Respiration; Exercise - physiology; Humans; Leg - blood supply; Magnetic Resonance Spectroscopy; Male; Muscle, Skeletal - metabolism; Myoglobin - physiology; Oxygen - metabolism; Oxygen Consumption; Partial Pressure; Rest - physiology; Skeletal Muscle And Exercise
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.2005.102327

Intracellular oxygen (O 2 ) availability and the impact of ambient hypoxia have far reaching ramifications in terms of cell signalling and homeostasis; however, in vivo cellular oxygenation has been an elusive variable to assess. Within skeletal muscle the extent to which myoglobin desaturates (deoxy-Mb) and the extent of this desaturation in relation to O 2 availability provide an endogenous probe for intracellular O 2 partial pressure ( P iO 2 ). By combining proton nuclear magnetic resonance spectroscopy ( 1 H NMRS) at a high field strength (4 T), assessing a large muscle volume in a highly efficient coil, and extended signal averaging (30 min) we assessed the level of skeletal muscle deoxy-Mb in 10 healthy men (30 ± 4 years) at rest in both normoxia and hypoxia (10% O 2 ). In normoxia there was an average deoxy-Mb signal of 9 ± 1%, which, when converted to P iO 2 using an O 2 /Mb half-saturation ( P 50 ) of 3.2 mmHg, revealed an P iO 2 of 34 ± 6 mmHg. In ambient hypoxia the deoxy-Mb signal rose to 13 ± 3% ( P iO 2 = 23 ± 6 mmHg). However, intersubject variation in the defence of arterial oxygenation ( S aO 2 ) in hypoxia ( S aO 2 range: 86–67%) revealed a significant relationship between the changes in S aO 2 and P iO 2 ( r 2 = 0.5). These data are the first to document resting intracellular oxygenation in human skeletal muscle, highlighting the relatively high P iO 2 values that contrast markedly with those previously recorded during exercise (∼2–5 mmHg). Additionally, the impact of ambient hypoxia on P iO 2 and the relationship between changes in S aO 2 and P iO 2 stress the importance of the O 2 cascade from air to cell that ultimately effects O 2 availability and O 2 sensing at the cellular level.