Relative effects of glucose and glutamine on reactive oxygen intermediate production by neutrophils

The energy source for neutrophils (PMNs) has long been believed to be glucose. However, it has been shown recently that PMNs use glutamine as well as glucose. Nevertheless, the comparative effects of glucose and glutamine on PMN function remain to be clarified. This study investigated the relative effects of glucose and glutamine on reactive oxygen intermediate (ROI) production by PMNs. In experiment 1, PMNs (1 x 10(6)/mL) isolated from healthy volunteers were incubated in RPMI 1640 medium containing neither glucose nor glutamine for 4, 12, 18, and 24 h at 37 degrees C. The medium was supplemented with 0 or 200 mg/dL (0 or 11 mM, respectively) glucose and glutamine (0, 0.5, 1, or 2 mM). PMN cell death was assessed on the basis of hypodiploid DNA by flow cytometry using propidium iodide DNA staining. ROI production by PMNs was determined by flow cytometry using dihydrorhodamine 123. In experiment 2, isolated PMNs were cultured in RPMI 1640 medium containing neither glucose nor glutamine. The medium was supplemented with glucose (0 or 11 mM) and a competitive inhibitor of glycolysis, 2-deoxy-D-glucose (2-DG; 0 or 20 mM). Each medium was supplemented with glutamine (0, 0.5, 1, or 2 mM) and incubated for 12 h at 37 degrees C. Then, ROI production by PMNs was measured. PMN cell death was not affected by glucose or glutamine in this experiment. In contrast, ROI production by PMNs was greater at 11 mM glucose than at 0 mM glucose at all incubation times studied. At 11 mM glucose, supplemental glutamine enhanced PMN ROI production after 18 and 24 h culture. In contrast, at 0 mM glucose, glutamine augmented ROI production by PMNs after 12 h as well as with 18 and 24 h incubations. PMN ROI production after 12 h culture was significantly greater at 11 mM glucose without 2-DG than at both 11 and 0 mM glucose with addition of 2-DG. In addition, supplemental glutamine enhanced ROI production by PMNs when 2-DG was added at 11 and 0 mM glucose. Glucose is essential for PMN ROI production. Under conditions of glucose depletion in vitro, glutamine is of importance in ROI production by PMNs, whereas the enhancing effect of glutamine on PMN ROI production is minor compared to that of glucose.