Abstract
For the development of amino acid derivatives as a new pancreas-scanning agent, comparative experiments were made on the in vivo incorporation of 18 kinds of 14C-labeled L-amino acid, and of D- and DL-forms of four selected radioactive amino acids into the trichloroacetic acid (TCA)-soluble and protein fractions of the pancreas and liver of mice. Among the L-forms tested, tryptophan, valine, methionine, and leucine, in this order of decreasing incorporation, showed a relatively high incorporation into the pancreas 30 min after intravenous injection. Pancreas/liver ratio of the radioactivity of methionine, valine, and leucine determined 15, 30, and 60 min after injection were 6 to 10. Although all of the amino acids were not predominantly high in pancreas/liver ratio compared with selenomethionine-75Se, the three amino acids seem a possible mother compound for introducing γ-emitters as a pancreas-scanning agent. In the TCA-soluble fraction of the pancreas, radioactivity of DL- or D-amino acids tested was higher than that of the corresponding L-amino acid. In particular, the almost whole radioactivity of D-leucine was found in the TCA-soluble fraction, and the activity due to D-leucine-14C itself. The incorporation of D-leucine into the pancreas was much the same as L-leucine. Based on these results, γ-radiating derivatives of amino acids might be useful as a new pancreas-scanning agent.
