Technetium radiopharmaceuticals: chemical characterization and tissue distribution of Tc-glucoheptonate using Tc-99m and carrier Tc-99.

The chemical structure of the kidney- and brain-imaging agent Tc-99m glucoheptonate has been established using the Tc-99 isotope. In a comparative study between Tc-99 and Tc-99m glucoheptonates, chromatographic, electrophoretic, and tissue distribution studies showed identical compounds in 0.9% NaCl. Optimal conditions for the formation of the Tc-99 glucoheptonate complex were investigated by uv and visible spectroscopy. The oxidation state of Tc-99 in the compound is V, measured by Sn2+ titration. The complex contains a Tc = O core and two glucoheptonate ligands (oxobis(glucoheptonato)technetate(V) anion (net charge: -1) in aqueous solution). NMR studies demonstrated two five-membered glucoheptonate rings, bidentate bound to Tc by the oxygens of the end carboxyl group and the adjacent hydroxyl group. The compound is stabilized by interaction between Tc-99 and one of the hydroxyloxygens of glucoheptonate at the vacant coordination site trans to the Tc = O core. Experiments with the reducing agent NaBH4 demonstrated the absence of Sn (II or IV) in the complex and a biological behavior independent of the reducing agent used.