Reversal of Carbon Monoxide-Cytochrome C Oxidase Binding by Hyperbaric Oxygen In Vivo

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Abstract
The classic mechanism of CO toxicity is tight binding of CO to hemoglobin which decreases the O2 carrying capacity of arterial blood and produces tissue hypoxia (1). In vitro effects, such as the shift of the oxygen hemoglobin dissociation curve to the left and CO binding to metallo-enzymes including cytochrome c oxidase are recognized but of uncertain physiological significance (2,3). Not all of the toxic effects of CO however, can be explained on the basis of the classic mechanism (4,5). Observations of CO toxicity at low HbCO may be the result of an effect of CO at the tissue level. Tissue uptake of CO in vivo has been demonstrated for myoglobin (4,5), but binding of CO to cytochrome c oxidase has not been confirmed previously in vivo. The purposes of this study were to document in vivo oxidation-reduction (redox) responses of brain cytochrome c oxidase to CO hypoxia, to identify formation and reversal of the CO-cytochrome a,a 3 ligand and to correlate those findings with the cardiovascular responses, measured HbCO, and arterial pH and blood gas values in a rat model of CO poisoning.

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