title: Relationship between complex stability and biokinetics of 99mTc-phosphate compounds.
abstract: The complex inertness of 99mTc-EHDP, -MDP, -PPi and -TriP was determined in vitro by means of protein binding of 99mTc after dilution in a phosphate-buffered albumin solution. Commercially available kits were used. In vitro, 99mTc-EHDP was found to be the most stable complex. The biodistribution of these agents was evaluated in the adult rat; here the less stable 99mTc-MDP proved to be the superior bone imaging agent. It is suggested that the complex inertness and the bone affinity are opposing properties of the 99mTc-phosphate compounds, because the complex must hydrolyse before the phosphate compound and technetium (IV) are deposited separately in bone. Hence, bone imaging with 99mTc-phosphate compounds demands a compromise concerning the stability of these complexes at low ligand concentrations, which among the investigated agents is best accomplished by 99mTc-MDP.
mesh_terms: D000818:Animals; D004164:Diphosphonates / Q000378:metabolism; D004355:Drug Stability; D005860:Germany, West; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D010710:Phosphates / Q000378:metabolism; D051381:Rats; D011933:Reagent Kits, Diagnostic; D013667:Technetium; D014018:Tissue Distribution; D006113:United Kingdom; D014481:United States
chemical_list: D004164:Diphosphonates; D010710:Phosphates; D011933:Reagent Kits, Diagnostic; D013667:Technetium