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In vivo mitochondrial oxygen tension measured by a delayed fluorescence lifetime technique |
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| Authors: | Mik Egbert G Johannes Tanja Zuurbier Coert J Heinen Andre Houben-Weerts Judith H P M Balestra Gianmarco M Stap Jan Beek Johan F Ince Can |
| Institution: | * Department of Physiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands † Department of Anesthesiology, Erasmus Medical Center, University of Rotterdam, Rotterdam, The Netherlands ‡ Department of Anesthesiology and Critical Care, University Hospital Tuebingen, Tuebingen, Germany § Department of Anesthesiology, University of Amsterdam, Amsterdam, The Netherlands ¶ Department of Medical Biochemistry, University of Amsterdam, Amsterdam, The Netherlands ‖ Center for Microscopical Research, Department of Cell Biology and Histology, University of Amsterdam, Amsterdam, The Netherlands *,* Laser Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands |
| Abstract: | Mitochondrial oxygen tension (mitoPO2) is a key parameter for cellular function, which is considered to be affected under various pathophysiological circumstances. Although many techniques for assessing in vivo oxygenation are available, no technique for measuring mitoPO2 in vivo exists. Here we report in vivo measurement of mitoPO2 and the recovery of mitoPO2 histograms in rat liver by a novel optical technique under normal and pathological circumstances. The technique is based on oxygen-dependent quenching of the delayed fluorescence lifetime of protoporphyrin IX. Application of 5-aminolevulinic acid enhanced mitochondrial protoporphyrin IX levels and induced oxygen-dependent delayed fluorescence in various tissues, without affecting mitochondrial respiration. Using fluorescence microscopy, we demonstrate in isolated hepatocytes that the signal is of mitochondrial origin. The delayed fluorescence lifetime was calibrated in isolated hepatocytes and isolated perfused livers. Ultimately, the technique was applied to measure mitoPO2 in rat liver in vivo. The results demonstrate mitoPO2 values of ∼30-40 mmHg. mitoPO2 was highly sensitive to small changes in inspired oxygen concentration around atmospheric oxygen level. Ischemia-reperfusion interventions showed altered mitoPO2 distribution, which flattened overall compared to baseline conditions. The reported technology is scalable from microscopic to macroscopic applications, and its reliance on an endogenous compound greatly enhances its potential field of applications. |
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