ASSAY OF RADIOGRAPHIC CONTRAST AGENTS IN MICE PLASMA AND TESTES BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A now buffer system is reported for the analysis of radiographic contrast agents (RCAs) sodium meglumine diatrizoate, lohexol, and lopamidol in mice plasma and testes, on a reversed-phase HPLC with UV detection. The buffer consisting of 0.1 M NaH2PO4, 0.2 mM Na2EDTA adjusted to pH 3.1 with orthophosphoric acid and 2.5-5.0 % acetonitrile (v/v) resolved RCA peaks for clear quantitation. The main advantages of this system are the ambient temperature of operation and direct sample injection without prior sample purification as required in the earlier procedures. Using this procedure, uptake and clearance kinetics of these RCAs were studied in mice plasma and testes, following iv injections via tall veins. The plasma levels of all the RCAs reached maxima between 5 and 15 min and dropped down sharply. At the end of 12 h they were virtually undetected (detection limits 0.64-0.71 mug/mL). The testicular levels also showed a similar trend and reached undetectable levels after 4 h. There were no signs of metabolism of these RCAs in plasma or testes. The present clearance kinetics in plasma compares very well with earlier reports of non-HPLC methods of assay.