[Potential application of DTPA for improving the image quality in radioimmunoscintigraphy with 111In labeled monoclonal antibodies].

Studies on application of diethylenetriamine-pentaacetic acid (DTPA) to decrease the non-specific localization of 111In-labeled antibodies (111In-MoAb) to the liver were performed. The transchelation of 111In to the molecule of M.W. 70,000-90,000 by the incubation of 111In-MoAb in human serum was inhibited by adding DTPA. These in vitro findings were also demonstrated by serum analysis after 111In-MoAb injection to the normal mice and postinjection of DTPA. By addition of DTPA, the uptake of 111In-MoAb by isolated rat hepatocytes was inhibited, but the 111In-release was unaffected. The addition of DTPA had no effect on uptake of 111In-MoAb and 111In-release in tumor cells. These results suggest that DTPA administration following 111In-MoAb injection may inhibit transchelation of 111In to transferrin or other serum proteins, so decrease non-specific liver localization of 111In and give rapid blood clearance.