Body distribution of C-methionine and FDG in rat measured by microPET

Compounds (18)F-fluorodeoxyglucose ((18)FDG) and (11)C-methionine ((11)C-MET) are radiodiagnostics frequently used in clinical Positron Emission Tomography (PET) as well in preclinical studies of various pathologies. The present study was focused on the comparison of biodistribution of both radiotracers in intact Wistar rats. The animals were scanned by microPET twice. The first scanning was done after (11)C-MET administration, the second scan followed 5-7 days later using (18)FDG. The radiotracers were injected into the tail vein of animals in isoflurane anesthesia. After a redistribution period, whole body scans were obtained using eXplore Vista SrT GE tomograph. Accumulation of the drugs in tissues was expressed in relative values (% ID/g) in selected regions of interest. As arbitrary reference tissue for drug accumulation, the sternoclavicular area was used. (18)C-MET was found remarkably cumulating especially in the liver, spleen and distal part of the gastrointestinal tract. The compound was accumulated in the liver 6.9±0.92 (mean±SEM) times more intensively than in the reference tissue. The respective value for spleen and cecum/colon was 5.62±0.81 and 3.56±0.14 times. Accumulation of (11)C-MET in other body parts including the brain and heart was very low and was apparently equal to the arbitrary tissue (0.13±0.01% ID/g). In the same animals (18)FDG (biontFDG) was remarkably cumulated especially in Harderian glands compared to arbitrary tissue background (11.02±1.00 times), heart (7.52±1.70 times), brain (6.14±0.37 times), and colon (5.68±0.31 times). (18)FDG accumulation in the liver, spleen and other organs was apparently not different from that found in the background (0.14±0.02% ID/g). The data obtained may serve as reference values in further microPET preclinical studies with (11)C-MET and (18)FDG under the given conditions.