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

We studied the biodistribution and tumour localization of 99Tcm-labelled-5-thio-D-glucose (99Tcm-TG). 5-Thio-D-glucose was labelled with 99Tcm by direct stannous ion reduction. The biodistribution of 99Tcm-TG was investigated in normal rabbits and in mice bearing experimental tumours. In rabbits, the plasma and clearance of 99Tcm-TG was 14.5 +/- 2.0 and 11.3 +/- 3.0 ml.min-1 respectively. Urinary excretion at 1 h was 53 +/- 5%. 99Tcm-TG was injected intravenously in mice bearing MC26 colon carcinoma and tissue samples were analysed by gamma scintillation counting at various times. Uptake of 99Tcm-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 99Tcm-TG in MX-1 human breast xenografted nude mice showed more persistent tumour uptake of 99Tcm-TG than 14C-2-deoxyglucose (14C-DG). 99Tcm-TG accumulated in the centre of the tumours; 14C-DG was decreased in this central region probably because of zones of infarction on necrosis. The discordance between the tumour uptake of 99Tcm-TG and 14C-DG indicates that 99Tcm-TG does not act like a glucose analog, suggesting 99Tcm-TG avidity for zones of infarction or necrosis. The further study of 99Tcm-TG in tumours and ischaemic injury is warranted.