Significance of 111In-DTPA chelate in renal radioactivity levels of 111In-DTPA-conjugated peptides

Hiromichi Akizawa, Yasushi Arano, Masaki Mifune, Akimasa Iwado, Yutaka Saito, Tomoya Uehara, Masahiro Ono, Yasushi Fujioka, Kazuma Ogawa, Yoshiaki Kiso, Hideo Saji

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Abstract

Metabolic studies of 111In-DTPA-labeled polypeptides and peptides showed that the radiolabeled (poly)peptides generated 111In-DTPA-adducts of amino acid that possess long residence times in the lysosomal compartment of the tissues where (poly)peptides accumulated. However, a recent study suggested that metal-chelate-methionine (Met) might possess in vivo behaviors different from metal-chelate adducts of other amino acids. In this study, to elucidate whether some biological characteristics of Met may accelerate the renal elimination rate of 111In-DTPA-adduct of Met into urine, 111In-DTPA-Met1-octreotide was synthesized and the renal handling of 111In-DTPA-Met was investigated using 111In-DTPA-L-Phe1-octreotide (Phe represents phenylalanine), which was reported previously, as a reference. Both 111In-DTPA-conjugated octreotide analogs were stable against 3-h incubation in murine serum at 37°C. Both 111In-DTPA-octreotide analogs also showed rapid clearance of the radioactivity from the blood and similar accumulation of the radioactivity in the kidney. No significant differences were observed in the renal radioactivity levels from 10 min to 24 h postinjection between the two. Metabolic studies indicated that 111In-DTPA-Met1-octreotide and 111In-DTPA-L-Phe1-octreotide generated 111In-DTPA-adducts of Met and Phe, respectively, as the final radiometabolites at similar rates. These findings suggested that the long residence times of the radioactivity in tissues after administration of 111In-DTPA-labeled peptides and polypeptides would be attributed to inherent characteristics of 111In-DTPA chelate.

Original languageEnglish
Pages (from-to)459-468
Number of pages10
JournalNuclear Medicine and Biology
Volume28
Issue number4
DOIs
Publication statusPublished - Jun 21 2001

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Keywords

  • In-DTPA chelate
  • In-DTPA-amino acid
  • In-DTPA-peptide
  • Renal radioactivity level

ASJC Scopus subject areas

  • Molecular Medicine
  • Radiology Nuclear Medicine and imaging
  • Cancer Research

Cite this

Akizawa, H., Arano, Y., Mifune, M., Iwado, A., Saito, Y., Uehara, T., Ono, M., Fujioka, Y., Ogawa, K., Kiso, Y., & Saji, H. (2001). Significance of 111In-DTPA chelate in renal radioactivity levels of 111In-DTPA-conjugated peptides. Nuclear Medicine and Biology, 28(4), 459-468. https://doi.org/10.1016/S0969-8051(01)00207-4