[Comparative distribution study of 14C labeled amino acids, glucose-analogue and precursor of nuclei acid, as tumor seeking agents].

As tumor-seeking agents, glucose analogues, natural amino acids, synthetic nonmetabolized amino acids, and precursor of nucleic acids, etc., labeled with positron emitter, such as 11C and 18F have been recently investigated. However, there are very few reports concerning comparative study of tumor uptake and tissue distribution of these agents. This preliminary paper describes comparative distribution and whole-body autoradiography of these agents. 14C labeled deoxy-2-fluoro-D-glucose (FDG), L-, DL-leucine, 1-aminocyclopentane carboxylic acid (ACPC), alpha-amino isobutyric acid (alpha-AIB), and thymidine were intravenously injected through tail vein into separate groups of the experimental animals. As the experimental animals, the mice with Ehrlich tumor and the rats with Hepatoma AH109A were used. Within 30 min after injection, FDG had the highest tumor uptake and tumor to tissue ratios, although FDG was inferior to ACPC and thymidine in related to tumor to heart, lung and brain ratios. However, the time course study indicated that tumor uptake of ACPC, alpha-AIB and D-leucine increased with time, whereas those of other agents decreased with time or reached a plateau. Thus, at 120 min after injection, ACPC had the highest tumor uptake and tumor to tissue ratios, although ACPC was inferior to FDG in related to tumor to blood, liver and pancreas ratios. Autoradiogram of ACPC showed very clear tumor image as well as that of FDG. The above data suggest that synthetic nonmetabolized amino acids, such as ACPC may be promising as tumor-seeking agents, when used with a single photon emission computed tomography, while glucose analogue such as FDG, are the best tumor-seeking agent, when used with a positron emission computed tomography.