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DETECTION OF WHOLE BODY OXIDATIVE STRESS IN URINE USING OXYGEN-18 LABELING
Slade, R., J. L. McKee, AND G. E. Hatch. DETECTION OF WHOLE BODY OXIDATIVE STRESS IN URINE USING OXYGEN-18 LABELING. Presented at SOT, San Francisco, March 25-29,2001.
DETECTION OF WHOLE BODY OXIDATIVE STRESS IN URINE USING OXYGEN-18 LABELING. R Slade, J L McKee and G E Hatch. PTB, ETD, NHEERL, ORD, USEPA, Research Triangle Park, NC, USA.
Reliable non-invasive markers for detecting oxidative stress in vivo are currently not available. We previously showed that rats breathing 18O-labeled molecular oxygen (18O2) during exposure to carbon tetrachloride (CCl4) had increased 18O incorporation into biochemical subfractions of the liver, suggesting that oxidative stress can be measured as 18O incorporation. The present study extends the previous study to determine whether 18O is detectable in urine following exposure to CCl4 and 18O2 . We injected Fischer 344 rats (male, 60 d old) with CCl4 (500 mg/kg i.p.) or corn oil vehicle, then exposed them to 20% 18O2 (in N2) for 1.25 h. Urine was collected for 5 days, and 18O incorporation was determined in the dry fraction of the urine. Exposure to 18O2 alone resulted in a large 18O incorporation: 920 g 18O/ g dry urine at 7 h post exposure decreasing to 430 g 18O/ g dry at 92 h. CCl4 treatment further increased the urinary 18O by 75% at 7 hr and 30% at 20 h postexposure. Intratracheal instillation of 18O-labeled water (H218O) in amounts similar to the metabolic production of H218O from breathing 18O2 led to accumulation of 18O in urine similar to that following 18O2 but peaking at 20 h postexposure. No significant differences were found in the amount of 18O in the lipid, macromolecular or solute fractions of the livers of rats killed at the end of the 5 day urine collection period. These results demonstrate that it is possible to detect labeled oxidation products in urine of rats exposed to CCl4 and 18O2. Further chemical identification of these products may assist in elucidating mechanisms for excretion of oxidized tissue constituents and help identify biomarkers of in vivo oxidative stress. (This abstract does not represent EPA policy)