Biochemical studies of the renal radiopharmaceutical compound dimercaptosuccinate. IV. Interaction of 99mTc-DMS and 99Tc-DMS complexes with blood serum proteins

As a crucial step towards understanding the mechanism of localisation of radiopharmaceuticals in specific target organs, the interaction of the radiopharmaceuticals ^99mTc-DMS and ⁹⁹Tc-DMS with blood serum proteins was studied. The interaction of ^99mTc-DMS radiopharmaceutical was examined from two aspects: total protein binding as well as specificity of binding to certain classes of proteins.After in vitro labelling of human sera with ^99mTc-DMS, the following values of bound radioactivity to total serum proteins were determined: 65%±3.2% by gel-filtration chromatography; 72%±4.6% by dialysis; while on the basis of precipitation by perchloric and trichloroacetic acid 72.7%±6.8% and 71%±2.3%, respectively. Distribution of ^99mTc-DMS or ⁹⁹Tc-DMS among serum proteins was analysed by agarose gel electrophoresis of the sera at pH 8.6 after in vivo and in vitro labelling of human sera with ^99m-Tc-DMS, while the same analysis was performed with ⁹⁹Tc-DMS complex after in vitro labelling of human and rat sera as well as after in vivo application to the rats.The results obtained demonstrate that carrier serum proteins investigated by agarose gel electrophoresis were in the migration zone of ₂-, ₁- and ₁-globulins, whereas the radioactivity found in the serum albumin zone was negligible. Interaction of both Tc-DMS complexes with proteins was very similar, and this conclusion was in good correlation with our previously obtained results in investigations concerning the biochemical behaviour of these complexes.