Human erythrocyte superoxide dismutase activity during deep diving

As the practical use of high pressure oxygen (HPO) in clinical medicine and the offshore industries accelerates, knowledge of its toxic nature becomes essential. In this study, divers' erythrocyte superoxide dismutase (SOD) activity was monitored during high pressure exposure and shown to decrease on average by 20% at depths greater than 150 m. Assay of total red cell SOD protein and activity established that the recorded SOD activity decrement was by loss of immuno-measurable enzyme. No evidence of intra-cellular Heinz bodies was observed. An increase of intra-membrane lipid peroxidation products, within physiological limits, was found, particularly in the denser cell fractions. Using previously in vivo pressure stressed cells, experiments at increasing O2 pressures educed that human red blood cells were oxygen "resistant" up to ten times the normal atmospheric pressure, 0.021 MPa (0.21 bar). Thereafter, a loss in SOD enzyme activity occurred with hemolysis during the in vitro decompression procedure.