In vitro effect of zinc on superoxide anion production by polymorphonuclear leukocytes of diabetic patients

We evaluated the ability of zinc to modulate the superoxide anion released by isolated, phorbol myristate acetate (PMA)-stimulated polymorphonuclear leukocytes (PMNs). In the presence of zinc at physiological level (20 mu mol/l), PMNs released 20% less superoxide anions than untreated cells, whereas at higher zinc concentration (200 mu mol/l), a 40%-increase in superoxide anion production was detected. The direction (suppression or stimulation) of superoxide anion generation was dependent upon extracellular zinc level and did not discriminate type 1 and 2 diabetic subjects from normal controls. The mechanism(s) of dose-dependent pro- and antioxidative effects of zinc on isolated PMNs in vitro as well as the implication of this finding for the modulatory effect of Zn on PMN-superoxide anion production in vivo need further investigation.