Influence of prosthetic radioiodination on the chemical and biological behaviour of chemotactic peptides labelled at high specific activity

OSCAR R. POZZI, ELISA O. SAJAROFF, MARTÍN M. EDREIRA

APPLIED RADIATION AND ISOTOPES

Año: 2006 vol. 64 p. 668 - 676

0969-8043

The influence of radioiodination made through prosthetic group N-succinimidyl-3-[131I]iodo-benzoate ([131I]SIB) on the behavior ofsmall peptides was investigated using as model the chemotactic hexapeptide Na-for-Nle-Leu-Phe-Nle-Tyr-Lys. No carrier added labeledpeptide was isolated by reverse-phase HPLC (RP-HPLC) with coupling efficiencies up to 59–75%. Biodistribution in normal andinfected C57 mice showed mainly a hepatobiliary clearance, a very low thyroid uptake and the highest uptake at the infection site was within 1 h of injection. Superoxide production and competitive binding assays studies in human polymorphonuclear leukocytes showed a preserved biological activity and high-affinity specific binding. However, the results indicated that the changes observed in the receptorbinding properties with an IC50 almost twice than the unlabeled peptide and the increasing in the hepatobiliary excretion could be the consequence of the increased lipophicity observed due to the presence of the prosthetic group together with a strong influence of the radioisotope per se.