On the nature of technetium compounds. 1. A semiquantitative biological model system to assay 99mTc-complexes/radiopharmaceuticals

Eleven different 99mTc compounds having some relevance in clinical nuclear medicine have been classified according to their localizing properties. The following classes of 99mTc compounds have been compared in a semiquantitative manner, using a Wistar strain rat model: liver and hepatobiliary agents such as Tc-phytate, Tc-sulfur colloid, reduced (SnII) TcO-4, and 99mTc-LIDA (dimethyl-IDA); bone agents like Tc-pyrophosphate, Tc-HEDP, Tc-EDTMP; kidney and bladder agents comprising Tc-DTPA, Tc-glucoheptonate, Tc-citrate, and TcO-4. The in vivo pharmacokinetic behavior lends itself to unified approach with respect to nature of 99mTc compounds. Most of the 99mTc complexes display an excretory type of pathway. These compounds were found to be relatively stable in aqueous solutions at room temperature (25 degrees-28 degrees C) for at least 2 h without any additives. Both paper chromatographic and biologic (tissue distribution) criteria, commonly used for quality assurance and control of 99mTc compounds, were employed to study these compounds.