Interactions of nitromusk parent compounds and their amino-metabolites with the estrogen receptors of rainbow trout (Oncorhynchus mykiss) and the South African clawed frog (Xenopus laevis)

Nitromusks, musk xylene (MX), musk ketone (MK) and musk moskene (MM) are sy nthetic fragrances. 4-Amino-MX (4X), 2-amino-MX (2X) and 2-amino-MK (2K) ar e nitromusk metabolites formed during the sewage treatment process and have been detected in effluent and surface water at concentrations four to 40 t imes higher than their parent compounds. To date, data to the aquatic toxic ity of nitromusk compounds are limited to the parent compounds and the dete rmination of acute and subacute effects in aquatic organisms. No data are a vailable regarding the potential endocrine modulating effects of these comp ounds and/or their metabolites in aquatic organisms. Therefore, the competi tive binding capability of nitromusks and their metabolites to the estrogen receptors (ER) in rainbow trout and xenopus was investigated. No binding o f MX, MK and MM to the ER of either species was observed. In contrast, bind ing to the ER was observed for 4X, 2X and 2K in both species. The IC50 (com petitive binding at the ER) of 2X in rainbow trout was 1.3 +/- 1.1 mM. In c ontrast, 4X, 2X and 2K bound to the xenopus ER with an IC50 of 30.8 +/- 28. 5, 12.9 +/- 10.3 and 70.1 +/- 88.3 mu M, respectively. (C) 1999 Elsevier Sc ience Ireland Ltd. All rights reserved.