In situ measurement of nitric oxide, superoxide and peroxynitrite during endotoxemia.

We report in vivo and ex vivo measurements of nitric oxide (electrochemical), ex vivo in situ measurements of superoxide (chemiluminescence) and peroxynitrite (chemiluminescence) and delineate the effect of endotoxemia on nitric oxide, superoxide and peroxynitrite release in aorta of rats. Nitric oxide release was measured in the aorta wall. An increase of nitric oxide concentration was observed immediately after administration of lipopolysaccharide (Escherichia coli serotype 0127: B8, 20 mg/kg), reaching a plateau ((50 nmol/L) after 180 +/- 50 seconds; the plateau was followed by decreasing nitric oxide concentration and its subsequent gradual small increase after 45 minutes. Superoxide and peroxynitrite production increased dramatically during endotoxemia. Superoxide concentration increased from 10 +/- 2 nmol/L to 28 +/- 3 nmol/L at one hour, and reached a 50 nmol/L plateau at 4 hours. The pattern of peroxynitrite release paralleled the pattern of superoxide release during the time course of endotoxemia. Diametrical alteration of nitric oxide and superoxide concentration with subsequent production of peroxynitrite may be a major cause of endothelial cell injury during endotoxemia.