Tumor uptake of radiolabeled pyrimidine bases and pyrimidine nucleosides in animal models —II. 6-[3H]-5-fluoro-2′-deoxyuridine

The short-term differential distribution of 6-[ 3H]-5-fluoro-2′-deoxyuridine (6-[ 3H]-5-FUdR) has been studied in vivo in the Ehrlich Ascites carcinoma (EACa) and Lewis Lung carcinoma (LLCa) tumor models in mice. Significant uptake of the nucleoside by the spleen, bone marrow, gastrointestinal tract and liver were observed, along with tumor:blood ratios of radioactivity in the region of 50:1. The maximum uptake of 6-[ 3H]-5-FUdR by the EACa and LLCa tumors represented 4.3% and 5.3% of the dose respectively. Approximately 60% of the administered dose was excreted in the urine within 6 h, and 80% of the dose was present in 72 h urine. Analysis of excretion data indicated that the fast elimination component half-times were 3.8 h (EACa) and 1.1 h (LLCa). Respective slow component half-times were 49 and 80 h.