Glutathione-dependent peroxidative metabolism in the alveolar macrophage

Abstract

Phagocytosis by rabbit alveolar macrophages (AM) is accompanied by increases in O₂ consumption, glucose oxidation, and H₂O₂ formation. Two aspects of the interrelations between these metabolic features of phagocytosis have been studied. First, the following evidence indicates that glutathione, glutathione reductase, and peroxidase serve as a cytoplasmic shuttle between H₂O₂ and NADPH-dependent glucose oxidation: (a) AM contain 5.9 mμmoles of reduced glutathione per 10⁶ cells and exhibit glutathione peroxidase and NADPH-specific glutathione reductase activity; (b) oxidized glutathione potentiates NADP stimulation of glucose oxidation; (c) an artificial H₂O₂-generating system stimulates glucose oxidation; (d) the cell penetrating thiol inhibitor, N-ethylmaleimide diminishes glucose oxidation. This effect largely depends on inhibition of the glutathione system rather than on inhibition of either H₂O₂ formation or enzymes directly subserving glucose oxidation. Second, three potential H₂O₂-generating oxidases have been sought. No cyanide-insensitive NADH or NADPH oxidase activity could be detected. D-amino acid oxidase activity was 0.48 ±0.07 U/10⁶ cells with D-alanine as substrate.