Accumulation of ^99mTc-Cysteine in Experimental Inflammatory Lesions in Comparison to ^99mTc-Glutamine and ^99mTc-HIG^[*]

Summary

Aim: The aim of this experimental work was to investigate the efficacy of ^99mTc-L-Cysteine (Cys) in scintigraphic visualization of inflammatory lesions in comparison to ^99mTc-L-glutamine (G), and ^99mTc-HIG. Methods: In mice abscesses were induced by intramuscular injection of turpentine. Six days later mice were injected with 3.7 MBq of each agent and sacrificed in groups of three at 1, 3, 6 and 24 h. Scintigrams were obtained with a gamma camera. The organs, some blood, abscesses, some muscle and urine were removed, weighed and counted in a gamma counter. Percentage of uptake by organs and per gram tissues and abscess/normal tissue concentration ratios were calculated. Experimental arthritis was produced in 6 New Zealand rabbits by intraarticular injection of ovalbumin. Four days later 37 MBq of ^99mTc-Cys and ^99mTc-HIG were each i.v. administered to 3 rabbits. Scintigrams obtained at 1, 3, 6, and 24 h demonstrated the arthritic joints very well. ROI’s over arthritic joints were compared to contralateral normal joints (A/C). Results: In mice the abscesses were well visualized on all scintigrams. The maximum abscess/muscle ratios were 5.21 ±1.09 (6 h), 3.73 ± 0.81 (3 h) and 5.98 ± 1.17 (24 h) and the maximum abscess/blood ratios were 3.46 ± 1.33 (24 h), 1.81 ± 0.10 (6 h) and 0.914 ± 0.351 (24 h) for ^99mTc-Cys, ^99mTc-G, and ^99mTc-HIG, respectively. In rabbits the maximum A/C ratios were 2.61 ± 0.53 (3 h) and 2.92 ± 0.99 (24 h) for ^99mTc-Cys and ^99mTc-HIG, respectively. Conclusion: our results indicate that ^99mTc-Cys is a promising agent for imaging inflammatory lesions. It is preferred to ^99mTc-HIG, because of higher concentration ratios attained earlier, lower blood background, lower cost and a simpler in-house preparation method.

Zusammenfassung

Ziel: Untersuchung der Effektivität von ^99mTc-L-Cystein (Cys) bei der szintigraphischen Darstellung entzündlicher Läsionen im Vergleich zu ^99mTc-L-Glutamin (G) und ^99mTc-markiertem humanem Immunglobulin (HIG). Methoden: In Mäusen wurden durch intramuskuläre Injektion von Terpentin Abszesse induziert. Sechs Tage später wurden die drei Substanzen, jeweils mit 3,7 MBq markiert, injiziert und die Tiere in Gruppen von drei nach 1, 3, 6 und 24 h geopfert. Szintigramme wurden mittels einer Gammakamera erstellt. Organe, Blut, Abszeß, Muskel und Urin wurden entnommen, gewogen und gezählt. %-Uptake/Organ und /g Gewebe und das Verhältnis Abszeß/Normalgewebe wurden berechnet. Weiterhin wurde bei sechs New Zealand-Kaninchen mittels intraartiku-lärer Injektion von Ovalbumin eine experimentelle Arthritis erzeugt. Vier Tage später wurden jeweils 37 MBq ^99mTc-Cys und ^99mTc-HIG i.v. injiziert. Szintigramme wurden abgeleitet 1, 3, 6 und 24 h und zeigten das entzündete Gelenk. Zählratenvergleiche mit dem normalen, kontralateralen Gelenk wurden mittels ROIs durchgeführt. Ergebnisse: Die Abszesse in Mäusen waren im Szintigramm gut darstellbar. Die Maxima Abszeß/Muskel betrugen für ^99mTc-Cys 5,21 ± 1,09, für ^99mTc-G 3,73 ± 0,81 und ^99mTc-HIG 5,98 ±1,17 und waren jeweils 6 bzw. 7 bzw. 3 oder 24 h p.i. nachweisbar, die Maxima Abszeß/Blut betrugen für ^99mTc-Cys 3,46 ± 1,33 für ^99mTc-G 1,81 ± 0,10 und für ^99mTc-HIG 0,914 ± 3,51 und traten jeweils 24, 6 bzw 24 h p.i. auf. Bei Kaninchen war das Verhältnis entzündetes/gegenseitiges Gelenk für ^99mTc-Cyss 2,61 ± 0,53 3 p.i. und für ^99mTc-HIG 2,92 ± 0,99 24 h p.i. Schlußfolgerung: Die Ergebnisse zeigen an, daß mit ^99mTc-Cys entzündliche Läsionen gut dargestellt werden können. Es ist dem ^99mTc-HIG überlegen, weil die höhere Konzentration früher erreicht wird, der Blutuntergrund niedriger ist sowie bei geringeren Kosten eine einfachere Herstellung im eigenen Heißlabor möglich erscheint.

Key words

^99mTc-Cysteine - ^99mTc-Glutamine - ^99mTc-HIG - abscess - arthritis

Schlüsselwörter

^99mTc-Cystein - ^99mTc-Glutamin - ^99mTc-HIG - Abszeß - Arthritis

^* Part of this work was presented at the 7th International Pharmaceutical Technology Symposium, Ankara, Türkiye, 12-14 Sept., 1994.

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