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FIGURE 4. Analysis of 18F-labeled metabolites in tumors. Shown are radiochromatograms (A and B) and corresponding UV chromatograms (C and D) obtained by gradient-elution HPLC of acid-soluble extract from Ward tumors. Tumors were harvested 2 h after intravenous injection of [18F]FU from rats pretreated with eniluracil (A and C) and not pretreated with eniluracil (B and D). UV absorption was measured for wavelengths 
214 nm. Percentages of radiolabel in each peak, as well as in the AIF, are indicated in (A and B). Aliquots of solutions containing authentic, nonradiolabeled samples of compounds indicated in the UV chromatograms were added to tumor extracts before injection for HPLC. FUrd = fluorouridine; FdUrd = fluorodeoxy-uridine; FUMP, FUDP, and FUTP = fluorouridine mono-, di-, and triphosphate, respectively; FdUMP, FdUDP, and FdUTP = fluorodeoxyuridine mono-, di-, and triphosphate, respectively; AIF = acid-insoluble fraction; FBAL = 
-fluoro-ß-alanine; FUPA = -fluoro-ß-ureido-propanoic acid; UDP = uridine diphosphate; UTP = uridine triphosphate; F– = fluoride ion. Standard chromatogram for [18F]F– (dashed lines in D) was determined separately. There was no evidence of free [18F]F– in studies shown.
