Interaction of 99mTc-radiopharmaceuticals with transport proteins in human blood

Interaction of a series of 99m Tc-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 99m Tc-radiopharmaceuticals, total protein binding was determined for thirteen 99m Tc-compounds (complexes of: HMPAO, GH, PAHIDA, MAG 3 , 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: α 1 -antitrypsin for 99m Tc-HMPAO, 99m Tc-DPD, 99m Tc(III)-DMSA renal agent, 99m Tc-GH, 99m Tc-DTPA, 99m Tc-PAHIDA and 99m Tc-EHIDA; albumin for 99m Tc(V)-DMSA tumorotropic agent and 99m Tc-MDP; transferrin for 99m Tc-phytate and 99m Tc-IODIDA; α 2 -globulin for 99m Tc-MAG 3 . Some agents were bound to two protein classes such as 99m Tc-PYP to α 1 -antitrypsin and transferrin; 99m Tc(III)-DMSA renal complex and 99m Tc-PAHIDA to α 1 -antitrypsin and α 2 -globulin. Some relationships between protein binding and biolocalization were noted for two 99m Tc-DMSA complexes and for three skeletal agents.