Unloaded Skeletal Muscle O_2 Uptake Decreases with Decreased Venous PO_2 at High-Frequency Stimulation

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Author(s)

Abstract

The aim of the present study was to clarify the effects of O<SUB>2</SUB> diffusion limitation resulting from hypoxic interventions on O<SUB>2</SUB> uptake (VO<SUB>2</SUB>) in unloaded (that is, near-zero initial force) and loaded skeletal muscle in a high-frequency stimulation. We measured VO<SUB>2</SUB>, muscle venous PO<SUB>2</SUB> (PV<SUB>O2</SUB>) and initial force in gastrocnemiusplantaris muscle in situ of anesthetized dogs: (1) during hypoxic hypoxia at 1 Hz tetanic stimulation, and (2) during hypoxia induced by the perfusion with high O<SUB>2</SUB>-affinity erythrocytes (having a low value of PO<SUB>2</SUB> at 50% saturation of hemoglobin (P<SUB>50</SUB>)) at 4 Hz twitch stimulation. Averaged unloaded VO<SUB>2</SUB> during normoxia was 10. 2 ml·min<SUP>-1</SUP>·100 g<SUP>-1</SUP> at averaged blood flow of 74 ml·min <SUP>-1</SUP>·100 g<SUP>-1</SUP> (n=6). Hypoxic hypoxia of a decreased O<SUB>2</SUB> delivery (arterial O<SUB>2</SUB> concentration × flow) significantly decreased both unloaded and loaded VO<SUB>2</SUB> with a decrease in PV<SUB>O2</SUB> (p<0.05). The unloaded VO<SUB>2</SUB> was reduced to 8.5 ml·min<SUP>-1</SUP>·100 g<SUP>-1</SUP>. Low P<SUB>50</SUB>-hypoxia decreased VO<SUB>2</SUB> at high and low initial force conditions with a decrease in PV<SUB>O2</SUB> (p<0.05) at the same O<SUB>2</SUB> delivery. If these decreases in VO<SUB>2</SUB> correspond with a decrease in VO<SUB>2</SUB> correspond with a decrease in VO<SUB>2</SUB> at zero initial force (unloaded VO<SUB>2</SUB>), the unloaded VO<SUB>2</SUB> value is calculated to be 7.57 ml·min<SUP>-1</SUP>·100 g<SUP>-1</SUP> from VO<SUB>2</SUB>-initial force data. Despite the different conditions of O<SUB>2</SUB> delivery, the unloaded VO<SUB>2</SUB> decreased by both hypoxia showed similar values. Thus the decreased unloaded VO<SUB>2</SUB> does not seem to be derived from only the limited O<SUB>2</SUB> delivery. Some other factors such as the limitation of O<SUB>2</SUB> diffusion may contribute to the decreased VO<SUB>2</SUB>.

Journal

  • The Japanese Journal of Physiology

    The Japanese Journal of Physiology 48(5), 347-354, 1998-10

    THE PHYSIOLOGICAL SOCIETY OF JAPAN

References:  17

Codes

  • NII Article ID (NAID)
    10008305352
  • NII NACSIS-CAT ID (NCID)
    AA00691224
  • Text Lang
    ENG
  • Article Type
    ART
  • ISSN
    0021521X
  • NDL Article ID
    4615127
  • NDL Source Classification
    ZS8(科学技術--医学--解剖学・生理学・生化学)
  • NDL Call No.
    Z53-D40
  • Data Source
    CJP  NDL  J-STAGE 
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