The antibiotic peptide 99'MTc-alafosfalin detects inflamed bowel in rats

Full text: Radiolabelled leucocyte scans are established as an accurate method of detecting inflammatory bowel disease and focal infection but involve complex in vitro cell labelling techniques. As antibiotic peptides accumulate at sites of inflammation, we studied the localisation of the antibiotic dipeptide 99mTc-alafosfalin in a rat model of colitis and compared it to the non-specific marker 99mTc-DTPA. Distal colitis was induced in female Sprague-Dawley rats (175g) 4 days following the rectal infusion of 1 ml trinitrobenzylsulphonic acid (80mg/ml; 30% aq. ethanol). Six colitic and 6 control rats were each injected intravenously with 5MBq 99mTc-alafosfalin (>90% radiolabelling efficiency) and 5MBq 99mTc-DTPA and organ and target site uptake measured by scintigraphy and quantitative counting of excised tissue (% injected dose/gram tissue) at 1 and 4 hours. Colitis was confirmed by histological examination of rectal specimens. The scans and tissue counts showed significant focal accumulation of 99mTc-alafosfalin in inflamed rectum compared to normal bowel (p<0.05). There was a sustained increase in the ratio of uptake in the inflamed to non- inflamed bowel at 1 and 4 hours (mean + S.E.) with 99mTc-alafosfalin compared to 99mTc-DTPA (p=0.03). Copyright (2002) The Australian and New Zealand Society of Nuclear Medicine Inc