ASCORBATE RECYCLING IN HUMAN NEUTROPHILS - INDUCTION BY BACTERIA

Ascorbate (vitamin C) recycling occurs when extracellular ascorbate is oxidized, transported as dehydroascorbic acid, and reduced intracellu larly to ascorbate. We investigated microorganism Induction of ascorba te recycling in human neutrophils and in microorganisms themselves. As corbate recycling oi-as determined by measuring intracellular ascorbat e accumulation. Ascorbate recycling in neutrophils was induced by both Gram-positive and Gram-negative pathogenic bacteria, and the fungal p athogen Candida albicans. Induction of recycling resulted in as high a s a 30-fold increase in intracellular ascorbate compared with neutroph ils not exposed to microorganisms, Recycling occurred at physiologic c oncentrations of extracellular ascorbate within 20 min, occurred over a 100-fold range of effector/target ratios, and depended. on oxidation of extracellular ascorbate to dehydroascorbic acid. Ascorbate recycli ng did not occur in bacteria nor in C. albicans, Ascorbate did not ent er microorganisms, and dehydroascorbic acid entry was less than could be accounted for by diffusion. Because microorganism recycling reduced dehydroascorbic acid to ascorbate, ascorbate recycling was absent bec ause or negligible entry of the substrate dehydroascorbic acid. Becaus e ascorbate recycling occurs in human neutrophils but: not in microorg anisms, it mag represent a eukaryotic defense mechanism against oxidan ts with possible clinical implications.