[In vitro comparative study of plasma protein binding of 99mTc-DTPA used in renal scintigraphy]

The radiopharmaceutical (99m)Tc-DTPA (diethylene-triamine-pentaacetic acid) is a tracer widely used in renal scintigraphy to assess glomerular filtration rate. The estimation of protein binding is very important due to its impact on clinical parameters biodistribution since only the free fraction is filtered by the kidney. A number of laboratory techniques have been developed to study protein binding. Precipitation and ultrafiltration are the mostly used techniques in pharmacology for studies of the binding between proteins and small molecules. The aim of this work is to apply and compare those two analytical methods in (99m)Tc-DTPA protein binding determination in vitro before in vivo application. The results obtained by precipitation with trichloroacetic acid are not enough reproducible, while those obtained by ultrafiltration seem more consistent and reproducible.