Validation of the protoporphyrin IX-triplet state lifetime technique for mitochondrial oxygen measurements in the skin

Mitochondrial oxygen tension can be measured in vivo by means of oxygen-dependent quenching of delayed fluorescence of protoporphyrin IX (PpIX). Here we demonstrate that mitochondrial PO2 (mitoPO2) can be measured in the skin of a rat after topical application of the PpIX precursor 5-aminolevulinic acid (ALA). Calibration of mitoPO2 measurements was done by comparison with simultaneous measurements of the cutaneous microvascular PO2 This was done under three different conditions: in normal skin tissue, in nonrespiration skin tissue due to the application of cyanide, and in anoxic skin tissue after the ventilation with 100% nitrogen. The results of this study show that it is feasible to measure the mitoPO2 after the topical application of ALA cream by means of the PpIX-triplet state lifetime technique.

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