Pneumocystis carinii: oxygen uptake, antioxidant enzymes, and susceptibility to oxygen-mediated damage.

The ability of Pneumocystis carinii obtained by alveolar lavage of rats with glucocorticoid-induced pneumocystosis to utilize molecular oxygen, the concentrations of selected antioxidant enzymes, and the susceptibility of P. carinii to in vitro killing by oxygen radical-generating systems have been evaluated. As expected of an organism which has been found to convert radiolabeled glucose to CO2, the parasite utilizes molecular oxygen. No evidence for pathways of oxygen utilization other than the cytochrome pathway was found; cyanide virtually abolished oxygen consumption. Although readily detectable levels of the antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase were present in the P. carinii preparations, only superoxide dismutase was present at levels that suggested that the activity was indeed a property of the parasite. Almost certainly, P. carinii does not possess effective concentrations of catalase. In addition, it was found that P. carinii is susceptible to the lethal actions of hydrogen peroxide and superoxide, but the parasite seems to be resistant to the effects of a hydroxyl radical-generating system.