Oxygen sensitivity of mitochondrial metabolic state in isolated skeletal and cardiac myocytes

Keith Neu Richmond, Steven Burnite, Ronald M. Lynch

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

In striated muscle the coupling of blood flow to changes in tissue metabolism is hypothesized to be dependent in part on release of vasodilating metabolic by-products generated when mitochondrial metabolism becomes O2 limited. Cytochrome oxidase, the terminal step in oxidative phosphorylation, is half-maximally saturated at <1 mmHg PO2 in isolated mitochondria. However, blood flow is regulated at tissue PO2 of ~20 mmHg. If the affinity of mitochondrial respiration for O2 were higher in vivo than in vitro, O2 limitation of mitochondrial metabolism near mean tissue levels could occur. In the present study the PO2 at which mitochondrial metabolism becomes inhibited (critical PO2) was measured for cardiac myocytes in suspension (1.1 ± mmHg) and single cells (1.0 ± 0.22 and 1.25 ± 0.22 mmHg in cardiac myocytes and rat spinotrapezius cells, respectively). These measurements are consistent with those from isolated mitochondria, indicating that vasodilators produced when oxidative phosphorylation becomes inhibited may be important for regulating blood flow only in highly glycolytic muscles or under conditions of severe O2 limitation.

Original languageEnglish (US)
Pages (from-to)C1613-C1622
JournalAmerican Journal of Physiology - Cell Physiology
Volume273
Issue number5 42-5
StatePublished - Dec 16 1997

Keywords

  • Blood flow regulation
  • Nicotinamide adenine dinucleotide fluorescence
  • Oxidative metabolism
  • Spectral imaging
  • Striated muscle

ASJC Scopus subject areas

  • Physiology
  • Cell Biology

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