INTERACTION OF TC-99M-RADIOPHARMACEUTICALS WITH TRANSPORT PROTEINS IN HUMAN BLOOD

Interaction of a series of Tc-99m-radiopharmaceuticals with human blood proteins was investigated from two aspects: total protein binding, and specificity of binding to certain classes of proteins. After in vitro labelling of human sera with Tc-99m radiopharmaceuticals, total protein binding was determined for thirteen Tc-99m-compounds (complexes of. HMPAO, GH, PAHIDA, MAG3, DTPA, PYP, MDP, DPD, EHIDA, IODIDA, Phytate and both complexes of DMSA) by a precipitation method (perchloric and trichloroacetic acid), dialysis and ultrafiltration. Selective binding to individual protein classes was determined by agarose gel electrophoresis after in vitro and in vivo labelling with the above-mentioned radiopharmaceuticals. The following carrier proteins were detected: alpha1-antitrypsin for Tc-99m-HMPAO, Tc-99m-DPD, Tc-99m(III)-DMSA renal agent, Tc-99m-GH, Tc-99m-DTPA, Tc-PAHIDA and Tc-99m EHIDA; albumin for Tc-99m(V)-DMSA tumorotropic agent and Tc-99m-MDP; transferrin for Tc-99m-phytate and Tc-99m IODIDA; alpha2-globulin for Tc-99m-MAG3. Some agents were bound to two protein classes such as Tc-99m-PYP to alpha1-antitrypsin and transferrin; Tc-99m(III)-DMSA renal complex and Tc-99m-PAHIDA to alpha1-antitrypsin and alpha2-globulin. Some relationships between protein binding and biolocalization were noted for two Tc-99m-DMSA complexes and for three skeletal agents.