Metabolic studies of [F-18-alpha-methyl]tyrosine in mice bearing colorectal carcinoma LS-180

Brain and tumor uptake of [F-18-alpha-methyl]tyrosine (F-18-AMT) and the in corporation into each of four fractions (lipid, RNA, DNA and protein) were investigated in mice bearing LS180 colorectal carcinoma, Homogenized tissue s were analyzed by the fractionation method into an acid-soluble fraction ( ASF) and an acid-precipitable fraction (APF). The APF was further investiga ted to assess the incorporation of F-18-AMT into each fraction. Incorporati on into four fractions of brain and tumor at 60 min post-injection was 20 a nd 12%, respectively; 10% of the activity was incorporated to lipid in brai n and 5% in tumor. There was 5, 2 and 2% incorporation with RNA, DNA and pr otein, respectively. Metabolites in ASF were analyzed by high-performance l iquid chromatography and thin-layer chromatography. There was only one radi oactive peak, which corresponded to F-18-AMT. The incorporation of F-18-AMT into lipid was twice that of F-18-AMT in tumor. The uptake of F-18-AMT in tissues was rapid and accomplished before 30 min, and then slowly diffused in blood. These results implied that F-18-AMT was metabolized to protein to only a small extent and trapped as intact F-18-AMT in cells up to 60 min. We conclude that F-18-AMT is a promising tracer for tumor imaging and quant ification of the transport rate using two-compartment models. [(C) 1999 Lip pincott Williams & Wilkins.].