title: Intracellular oxygen tension limits muscle contraction-induced change in muscle oxygen consumption under hypoxic conditions during Hb-free perfusion.
abstract: Under acute hypoxic conditions, the muscle oxygen uptake (mV˙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 mV˙O2under hypoxic conditions at the peripheral tissue level. Therefore, this study set out to test the hypothesis that the restriction in mV˙O2is regulated by the net decrease in intracellular oxygen tension equilibrated with myoglobin oxygen saturation (∆PmbO2) 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 O2gas: 95.0%O2, 71.3%O2, and 47.5%O2The 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 (SmbO2), and the PmbO2was then calculated based on the SmbO2and the O2dissociation curve of the Mb. The SmbO2and PmbO2at rest decreased with the decrease in O2supply, and the muscle contraction caused a further decrease in SmbO2and PmbO2under all O2conditions. The net increase in mV˙O2from the muscle contraction (∆mV˙O2) gradually decreased as the ∆PmbO2decreased during muscle contraction. The results of this study suggest that ΔPmbO2is a key determinant of the ΔmV˙O2.
authors.affiliation: Faculty of Health and Sports Science, Doshisha University, Kyotanabe, Japan.|Faculty of Human Sciences, Kanazawa University, Kanazawa, Japan.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Takakura
authors.affiliation: Faculty of Human Sciences, Kanazawa University, Kanazawa, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Ojino
authors.affiliation: Department of Biochemistry and Molecular Medicine, University of California Davis, Davis, California.
authors.forename: Thomas
authors.initials: T
authors.lastname: Jue
authors.affiliation: Faculty of Human Sciences, Kanazawa University, Kanazawa, Japan.|Department of Cell Biology, School of Medicine Johns Hopkins University, Baltimore, Maryland.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Yamada
authors.affiliation: Faculty of Human Sciences, Kanazawa University, Kanazawa, Japan.|Department of Health Promotion Science, Tokyo Metropolitan University, Hachioji, Japan.
authors.forename: Yasuro
authors.initials: Y
authors.lastname: Furuichi
authors.affiliation: Faculty of Sport and Health Science, Ritsumeikan University, Kusatsu, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hashimoto
authors.affiliation: Department of Physiology, Aichi Medical University, Nagakute, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Iwase
authors.affiliation: Faculty of Human Sciences, Kanazawa University, Kanazawa, Japan masudak@staff.kanazawa-u.ac.jp.
authors.forename: Kazumi
authors.initials: K
authors.lastname: Masuda
mesh_terms: D000818:Animals; D015687:Cell Hypoxia; D005947:Glucose; D006614:Hindlimb; D000860:Hypoxia / Q000378:metabolism*; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000378:metabolism*; D009211:Myoglobin / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption; D051381:Rats; D017208:Rats, Wistar; D014325:Tromethamine
chemical_list: C074097:Krebs-Henseleit solution; D009211:Myoglobin; D014325:Tromethamine; D005947:Glucose; D010100:Oxygen
keywords: Hindlimb perfusion; hypoxia; intracellular oxygen tension; myoglobin