Altered Function of Cat Carotid Body Chemoreceptors in Prolonged Hyperoxia

Abstract

On thermodynamic grounds the mitochondrial redox catalysts are likely to be oxidized by molecular oxygen. Accordingly, their rates of auto-oxidation are enhanced by increasing oxygen pressure, generating oxygen radicals. These radicals are ordinarily removed by the protective enzymes such as Superoxide dismutase. Overproduction of the naturally occuring oxygen radicals during hyperoxia can overwhelm the enzymatic removal systems, resulting in a net accumulation of these free radicals (Fridovitch, 1983). Since oxygen chemoreception in the peripheral chemoreceptors depends on a reaction or interaction with oxygen, and since the chemosensory discharge continues to be suppressed by PO₂ increases even in the hyperoxic range, we hypothesised that the chemoreceptor tissue may be specifically sensitive to oxygen radicals.