TUMOR LOCALIZING AGENTS .8. RADIOIODINATED PHENYLALANINE ANALOGS

Use of the currently available l‐selenomethionine‐75Se for external pancreatic photoscanning is limited by the long biological half‐life of the amino acid and the dense radiations arising from high liver concentrations of the compound. The present study was initiated in an effort to find superior pancreas‐specific photoscanning agents. The approach presented here is based upon the previously established specificity of natural amino acids for pancreatic tissue. In the anticipation that this specificity might extend to other radiolabeled synthetic amino acids, ortho‐, meta‐, and para‐iodophenylalanine‐125I and the corresponding acetylated derivatives were synthesized for tissue distribution analysis. All three iodophenylalanine‐125I isomers showed a specificity for pancreatic tissue in mice but not in dogs. Acetylation of the radioiodinated amino acids caused no qualitative changes in the tissue distribution results in either species. Copyright © 1968 Wiley‐Liss, Inc., A Wiley Company