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 lae6is) AbstractNitromusks, 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 IC 50 (competitive binding at the ER) of 2X in rainbow trout was 1.3 91.1 mM. In contrast, 4X, 2X and 2K bound to the xenopus ER with an IC 50 of 30.8928.5, 12.9910.3 and 70.1988.3 mM, respectively.

Musk xylene (MX), musk ketone (MK) and musk moskene (MM) are synthetic nitro-containing fragrances. Due to their inherent lipophilicity and environmental persistence, they are frequently detected in environmental samples and especially in aquatic ecosystems. Despite this, the current environmental toxicity database of nitromusks is limited. Although nitromusks have been shown to accumulate in aquatic organisms, little is known about their potential developmental effects in the respective aquatic species. To investigate the developmental toxicity of these compounds to amphibians and fish, early lifestages of xenopus (Xenopus lae6is) and zebrafish (Danio rerio) were exposed to three nitromusks for 96 h to examine the developmental effects of these compounds in the two species. Nitromusk body concentration measurements were carried out in parallel for correlation with potential developmental effects. No increased mortality, malformation or growth inhibition was observed in either species following 96-h exposure to 400 mg/l MX, MK and MM. However, an approximately 20% reduced viability was observed in xenopus larvae when exposed to 400 mg/l MX, MK and MM for 11 days. Xenopus and zebrafish exposed to 10, 153, 871 and 1637 mg/l 14 C-MX for 96 h resulted in whole-body concentrations of 0.7 90.1, 11.191.1, 38.79 1.9 and 76.3 9 18.3 mg/g, and 4.3 90.6, 73.3911.8, 440.0972.7 and 664.09 47.7 mg/g wet body weight, respectively. Exposure of xenopus larvae to 400 mg/l MX, MK and MM for 11 days, resulted in whole body concentrations (extrapolated from gas chromatographic determinations) of 4700 95000, 13009 300 and 46009 4800 mg/g wet weight for MX, MK and MM, respectively. The latter toxicity results, in conjunction with the fact that the concentrations used for the above experiments were between 400-and 10 000-fold higher than those detected in the environment, suggest that environmental concentrations of nitromusks are not hazardous for early lifestages of fish and amphibians.

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