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 synthetic fragrances. 4-Amino-MX (4X), 2-amino-MX (2X) and 2-amino-MK (2K) are nitromusk metabolites formed during the sewage treatment process and have been detected in effluent and surface water at concentrations four to 40 times higher than their parent compounds. To date, data to the aquatic toxicity of nitromusk compounds are limited to the parent compounds and the determination of acute and subacute effects in aquatic organisms. No data are available regarding the potential endocrine modulating effects of these compounds and/or their metabolites in aquatic organisms. Therefore, the competitive binding capability of nitromusks and their metabolites to the estrogen receptors (ER) in rainbow trout and xenopus was investigated. No binding of MX, MK and MM to the ER of either species was observed. In contrast, binding to the ER was observed for 4X, 2X and 2K in both species. The IC50 (competitive binding at the ER) of 2X in rainbow trout was 1.3±1.1 mM. In contrast, 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 μM, respectively