Method for Tracing Oxygen-18 in Vivo: Application to Ozone Dosimetry in Animals
The lack of a long-lived radioactive isotope of oxygen has impeded tracing studies involving oxygen labels. The Environmental Protection Agency (EPA) has investigated new methods for tracing oxygen-18 in vivo 1,2 to detect reaction products in inhaled ozone (O3) and other pollutants in tissues and for investigating mechanisms of toxicity. This report describes a technique for exposing experimental animals to oxygen-18 labeled ozone (18Oз), then converting oxygen present in respiratory tissues to CO2 prior to isotope ratio mass spectrometry to determine the enrichment of oxygen-18 (18O) in the tissue. Since O3 toxicity is believed to arise from either direct reaction of O3 with tissue constituents or from initiation of free radical-induced autoxidations, the 18O-tracing techniques should be applicable to detecting these as well as other types of oxygen reactions. It was hoped that this approach would be more generally applicable than approaches in which a specific reaction product was extracted then analyzed for the presence of the label.
KeywordsEnvironmental Protection Agency Isotope Ratio Mass Spectrometry Fractional Abundance Respiratory Tissue Tissue Constituent
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