Biodistribution of 99Tcm-labelled 5-thio-D-glucose

We studied the biodistribution and tumour localization of Tc-labelled-5-thio-D-glucose (Tc-TG). 5-Thio-D-glucose was labelled with Tc by direct stannous ion reduction. The biodistribution of Tc-TG was investigated in normal rabbits and in mice bearing experimental tumours. In rabbits, the plasma and clearance of Tc-TG was 14.5 ± 2.0 and 11.3 ± 3.0 ml·min respectively. Urinary excretion at 1 h was 53 ± 5%. Tc-TG was injected intravenously in mice bearing MC26 colon carcinoma and tissue samples were analysed by gamma scintillation counting at various times. Uptake of Tc-TG in tumour at 1 and 3 h was 1.6 ± 0.3% and 1.2 ± 0.3%; the tumour to muscle ratios were 2.7:1 and 4:1 respectively. The autoradiographic biodistribution of Tc-TG in MX-1 human breast xenografted nude mice showed more persistent tumour uptake of Tc-TG than C-2-deoxyglucose (C-DG). Tc-TG accumulated in the centre of the tumours; C-DG was decreased in this central region probably because of zones of infarction on necrosis. The discordance between the tumour uptake of Tc-TG and C-DG indicates that Tc-TG does not act like a glucose analog, suggesting Tc-TG avidity for zones of infarction or necrosis. The further study of Tc-TG in tumours and ischaemic injury is warranted.