BACKGROUND: Our goal was the efficient labelling of highly purified human gammaglobulin. This radioactive protein fraction can be used as a basic compound of radiopharmaceutical formulation for inflammation lesion diagnosis. This application was experimentally illustrated in animal models with artificially induced inflammatory lesions after turpentine oil injection into mouse leg muscle. MATERIALS AND METHODS: RESULTS: Efficiency of technetium99m Tc human gammaglobulin labelling (pH 7.4, temp. 37 degrees C) was strictly dependant on ligand and coligand presence in the reaction mixture. Labelling of IgG molecules without any supplements resulted in very low efficiency, never exceeding the range of 5%. Presence of EDTA or hydrazine nicotinamide (HYNIC) conjugated with IgG increased radiolabelling efficiency to 50%. IgG-HYNIC derivative in EDTA presence enables us to reach value above 95% radiochemical purity. Stability of IgG-HYNIC derivative labelled with technetium (99m) Tc decreased rapidly in serum in time--up to 70% of initial value in 30 minutes and only 20% during further 4 hr incubation. This means that as much as 80% of radiotracer present in IgG molecules has been dissociated during incubation with serum. This forced us to find proper conditions for improving the stability of radioactive IgG-HYNIC conjugate in circulating serum for at least six hours. It was achieved by using a reaction medium supplement with divalent metal cations in the following compounds: MgCl2, CoSO4, Cu (NO3)2 and FeCl2 in equimolar ratio to EDTA. Scintigraphy of (99m)Tc gammaglobulin in artificially induced inflammatory lesions of mouse thigh muscle showed a 4 times higher accumulation of the tracer after 6 hours post injection, and 6 times higher after 24 hours. CONCLUSIONS: A human gammaglobulin derivative ( hIgG-HYNIC) labelled with technetium (99m)Tc by indirect method with high radiochemical purity can be a basic compound of formulation for infection/ inflammation scintigraphy.
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