Protein-binding and urinary excretion of 99mTc(Sn)-MDP and 99mTc-MDP

The binding of 99mTc(Sn)-MDP complexes to human serum albumin and other blood proteins determined with gel chromatography and ultrafiltration

The binding of 99mTc(Sn)-MDP to human serum albumin and other blood proteins was investigated by gel chromatography and ultrafiltration. During gel chromatography dissociation of the 99mTc(Sn)-MDP-protein complex occurs: thus, it is not a suitable technique for the determination of protein binding. The values found with ultrafiltration have to be corrected for non-ultrafiltrable TcO2.nH2O. From the corrected values it can be concluded that binding of 99mTc(Sn)-MDP to blood proteins does not play a role in the biodistribution.

Binding of 99mTc(113Sn)-MDP to human serum albumin. The influence of various technetium, tin, and MDP concentrations

The HSA-binding of 99mTc incubated as 99mTc(113Sn)-MDP depends in vitro on the presence of competing anions normally present in plasma and on the MDP and Tc concentration, but is independent of the Sn concentration. The HSA-binding of 113Sn depends on the MDP and Sn concentration; not on the Tc concentration. 99mTc(Sn)-MDP binds to HSA as a unit. The binding of 99mTc(Sn)-MDP to plasma proteins in vivo is much lower as calculated from in vitro experiments because of competition between 99mTc(Sn)-MDP and endogenous anions for the same binding-sites.