[Long term biokinetics of 169Yb following injection as citrate, hydroxyethylethylenediaminetetraacetate and nitrilotriacetate].

169Yb complexes with known biokinetics in tumour-bearing mice up to 48 h p.i. were injected into healthy mice to study the radionuclide biodistribution in various organs and tissues for 672 h after injection, in order to obtain reliable biokinetic data in an animal model, not affected by tumour-growth, as a basis for the calculation of biological half-life and dose distribution. The results demonstrated the existence of at least two components with different biological half-lives in the organs and tissues investigated. The effective half-lives of these components decreased with increasing stability of the complexes administered. The effective half-life of the fast component was a few hours and that of the slow one between about 200 and 800 h.