Search for polynuclear pentavalent technetium complex of dimercaptosuccinic acid [Tc(V)-DMS] tumour localization mechanism

To search for the tumour localization mechanism of Tc(V)-DMS, a polynuclear pentavalent technetium complex of dimercaptosuccinic acid [Tc(V)-DMS], the development of medullary thyroid carcinoma (MTC) bearing mouse model was considered. Subcutaneously transplanted tumour was allowed to grow for 2, 4 and 6 weeks, and the influence of the tumour stage on the biodistribution of Tc(V)-DMS was screened. High radioactivity uptake in the tumour tissue was observed, and this accumulation showed a direct correlation with tumour growth and calcitonin secretion, the MTC marker detectable in the blood serum. The gathered data implicated some calcitonin-related factors as the mediator in the Tc(V)-DMS localization; participation of a phosphate-like oxoanion, TcO₄^3–, is strongly suggested not only by the high radioactivity accumulation in the calcitonin-producing tumour but also by the accumulation in the bones of this model animal.Offprint requests to: A. Yokoyama