Activated polymorphonuclear leucocytes consume vitamin C.

Polymorphonuclear leucocytes (PMN) are known to produce superoxide and other oxygen derivatives upon activation as part of their microbicidal armory. Here we report that extracellular ascorbate is effectively oxidised by activated but not by resting human PMN in vitro. The oxidation of ascorbate is mainly caused by the superoxide that is generated by the activated cells, as shown by its effective inhibition by superoxide dismutase. However, myeloperoxidase, which may generate hypochlorite, also contributes to a significant extent. Ascorbate reduces superoxide to peroxide, as indicated by measurements of the stoichiometry of ascorbate and oxygen consumption. These results support the notion that extracellular ascorbate may serve as an important physiological protecting agent against oxygen radical damage in inflammation.