Richmond 1999 Am J Physiol

Richmond KN, Shonat RD, Lynch RM, Johnson PC (1999) Critical P_O₂ of skeletal muscle in vivo. https://doi.org/10.1152/ajpheart.1999.277.5.H1831

» Am J Physiol 277:H1831-40. PMID: 10564137 Open Access

Richmond KN, Shonat RD, Lynch RM, Johnson PC (1999) Am J Physiol

Abstract: The main purpose of this study was to determine the interstitial oxygen tension at which aerobic metabolism becomes limited (critical P_O₂) in vivo in resting skeletal muscle. Using an intravital microscope system, we determined the interstitial oxygen tension at 20-micrometer-diameter tissue sites in rat spinotrapezius muscle from the phosphorescence lifetime decay of a metalloporphyrin probe during a 1-min stoppage of muscle blood flow. In paired experiments NADH fluorescence was measured at the same sites during flow stoppage. NADH fluorescence rose significantly above control when interstitial P_O₂ fell to 2.9 ± 0.5 mmHg (N = 13) and was not significantly different (2.4 ± 0.5 mmHg) when the two variables were first averaged for all sites and then compared. Similar values were obtained using the abrupt change in rate of P_O₂ decline as the criterion for critical P_O₂. With a similar protocol, we determined that NADH rose significantly at a tissue site centered 30 micrometer from a collecting venule when intravascular P_O₂ fell to 7.2 ± 1.5 mmHg. The values for critical interstitial and critical intravascular P_O₂ are well below those reported during free blood flow in this and in other muscle preparations, suggesting that oxygen delivery is regulated at levels well above the minimum required for oxidative metabolism. The extracellular critical P_O₂ found in this study is slightly greater than previously found in vitro, possibly due to differing local conditions rather than a difference in metabolic set point for the mitochondria.

• Bioblast editor: Gnaiger E

Labels: MiParea: Respiration, Exercise physiology;nutrition;life style

Stress:Hypoxia Organism: Rat Tissue;cell: Skeletal muscle

Regulation: Oxygen kinetics, Redox state

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