Spin label oximetry to assess extracellular oxygen during myocardial ischemia.

Abstract

We describe real-time measurement of myocardial oxygen consumption during ischemia in the intact heart. Measurement of extracellular oxygen concentration during myocardial ischemia by spin label oximetry has been limited by ischemia-induced reduction of the neutral, water-soluble nitroxide TEMPONE. We have overcome this problem by encapsulating the nitroxides. Isolated immature (7-10 d old) rabbit hearts (n = 8) were perfused aerobically within the cavity of a loop gap resonator with bicarbonate buffer containing an oxygen-sensitive, lipid-soluble nitroxide (14N-TEMPO laurate in FC-43 perfluorocarbon micelles) and a much less oxygen-sensitive and positively charged nitroxide (15N-TEMPO choline in multilamellar vesicles) as an internal standard. The ratio of the ESR signal amplitudes of these nitroxides was used as a sensitive index of oxygen concentration. Sequestration of the nitroxides decreased their reduction rate by ascorbate in comparison with nonsequestered nitroxides. Hearts were subjected to 60 min of global no-flow ischemia at 20 degrees C. Extracellular oxygen content (mean +/- SD) during aerobic perfusion was 1195 +/- 55 mumol/liter. The electron spin resonance signal from TEMPO laurate increased with the onset and progression of ischemia, consistent with a decrease in extracellular oxygen, while the signal for TEMPO choline was relatively unchanged. Extracellular oxygen content after 40 and 60 min of ischemia was reduced to 393 +/- 27 mumol/liter (p < .05) and 61 +/- 5 mumol/liter (p < .05), respectively. We conclude that spin-label oximetry can directly and precisely measure myocardial oxygen consumption at constant temperature during ischemia in the intact heart.

• Authors: J E Baker, W Froncisz, J Joseph, B Kalyanaraman
• Journal: Free radical biology & medicine (Free Radic Biol Med) Vol. 22 Issue 1-2 Pg. 109-15 ( 1997) ISSN: 0891-5849 [Print] United States
• PMID: 8958135 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Free Radicals
• Liposomes
• Micelles
• Nitrogen Oxides
• Spin Labels
• Triacetoneamine-N-Oxyl
• nitroxyl
• Oxygen

Topics

• Animals
• Electron Spin Resonance Spectroscopy
• Feasibility Studies
• Free Radicals
• In Vitro Techniques
• Liposomes
• Micelles
• Myocardial Ischemia (blood)
• Nitrogen Oxides
• Oxidation-Reduction
• Oximetry (methods)
• Oxygen (blood)
• Perfusion
• Rabbits
• Spin Labels
• Triacetoneamine-N-Oxyl (analysis)