The study of the bioconcentration of silver nanoparticles (AgNPs) is important to fully understand their hazard potential in the aquatic environment. We synthesized AgNPs radiolabeled with silver isotopes (Ag-110m) to quantify the bioconcentration of AgNPs coated with citrate (AgNPs-CIT) and polyvinylpyrrolidone (AgNPs-PVP) in Japanese medaka, and to investigate the biodistribution of silver in organs, which were compared with (AgNO3)-Ag-110m. BCF values were determined to be 39.8 +/- 7.4, 42.5 +/- 5.1 and 116.4 +/- 6.1 L kg(-1) for AgNPs-CIT, AgNPs-PVP and AgNO3, respectively. The release of more silver ions in AgNPs-PVP contributed to a different kinetic uptake pattern with AgNPs-CIT, which was similar to that of AgNO3. Bioconcentrated AgNPs in medaka were not observed to be eliminated, independent of surface coating differences, similarly to AgNO3. There was no difference in biodistribution in each organ before and after depuration in two types of AgNPs and AgNO3, all of which were mainly concentrated in the liver. This study quantified the bioconcentration and distribution of AgNPs and AgNO3 more precisely by utilizing a silver isotope, which is helpful in monitoring the toxicity of AgNPs to Japanese medaka. (C) 2014 Elsevier B.V. All rights reserved.