Biodistribution of 99mTc-labelled Low Molecular Peptides and Proteins in an AnimalModel of Inflammation

Overview

The aim of this study was to evaluate accumulation of the low molecular peptides and proteinslabelled with 99mTc in rat inflammatory/infection foci. Peptides (human leukocyte dialysate – HLD,thymosin fraction 5 – TF5, aprotinin – APT), proteins (human IgG – HIG) were labelled with 99mTcusing a redox polymer. The labelling efficiency was evaluated using paper, TLC and/or columnchromatography and electrophoresis. The biodistribution of the labelled substances was evaluatedin Wistar rats with Staphylococcus aureus infection or with sterile kaolin suspension-inducedinflammation in the left inguinal region 24 h after abscess induction.Accumulation of 99mTc activitywas determined both by external gamma camera imaging and by counting dissected tissues 1–4hours after administration. The evaluated peptides and proteins show a high labelling efficiency(99mTc-HLD>98 %, 99mTc-TF5>95 %, 99mTc-APT>98 %, 99mTc-HIG>95 %). Use of redox polymerfor labelling raises the stability of 99mTc-labelled substances so that the labelling efficiency remainsto be virtually the same (95–98 %) after 8 hours at least. In experimentally induced inflammation,the amount of 99mTc-peptides and 99mTc-HIG activity accumulated is 2.5–6.5 and 5.3–10.6 times,respectively, that in control tissue.A comparison of two types of model inflammations (inflammation induced by kaolin and Staphylococcus-induced inflammation) revealed the values measured with99mTc-peptides are more than a double that induced by kaolin suspension. The studied lowmolecular peptides labelled with 99mTc allowrapid localisation of infection foci in the animalmodel.99mTc labelled HIG seems to be useful for the detection of both infections and inflammatory lesions.

Key words:
technetium (99mTc) – inflammation – biodistribution – peptides – proteins