Mechanism of the Toxic Effects of Hyperbaric Oxygen

Abstract

THE mechanism of the toxic effects of hyperbaric oxygen has long been a subject of discussion and Haugaard¹ has summarized the evidence in favour of the view that the toxicity is due to oxidation of sulphydryl groups. More recently, however, Chance et al.² observed that 11–17 atm. of oxygen selectively inhibit the energy-linked reduction by succinate of nicotinamide-adenine dinucleotide (NAD). Because this inhibition occurs much more rapidly than oxidation of sulphydryl groups, Chance et al. suggested the energy-linked reduction of NAD by succinate as the site of the toxic effects of hyperbaric oxygen. The oxygen pressures used by Chance, however, were much greater than those customarily used therapeutically³—that is 3 atm. Because toxicity is also observed at these pressures, it seemed desirable to examine the effects of oxygen at 3 atm. on the energy-linked reduction of NAD by succinate.