[The effect of Ca-diethylenetriamine pentaacetate on the bio-behavior of tumor-affine metal complexes].

The complexon CaDTPA was injected into tumour-bearing mice in concentrations of 0.05, 0.1, 0.3, and 0.6 mole/l (pH:6) 30 min after the 169Yb-injection. 100 microliters of a 0.3 M CaDTPA solution were injected at different time points (simultaneously, 2, 5, 10, 20, 30, 40 and 50 min, 1, 1.25, 1.5, 2.5 and 10 h) after 169Yb-citrate injection. The animals were killed 24 h after radionuclide administration. A strong radioactivity decrease was observable 24 h p.i. not only in blood, liver, spleen, muscle and bone but also in the tumour if CaDTPA was administered within the first 2 h after ytterbium injection. Thereafter no change in radioactivity could be achieved by DTPA. A time phase in which the Yb could be eliminated from the tissues by means of DTPA (time intervals < 2 h) was distinguishable from a time phase in which it was not attainable for DTPA (time intervals > 5 h). This indicates that the incorporation of Yb into the cells is completed after 5 h and that the metals are intracellularly bound, probably to the lysosomes. Improvements of the scintigraphic tumour detection cannot be expected from the use of complexons.