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Nitro Musk Adducts of Rainbow Trout Hemoglobin: Dose-Response and Toxicokinetics Determination By Gc-Nici-MS for a Sentinel Species

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Abstract:Rainbow trout and other fish species can serve as 'sentinel' species for the assessment of ecological status and the presence of certain environmental contaminants. As such they act as bioindicators of exposure. Here we present seminal data regarding dose-response and toxicokinetics of trout hemoglobin adduct formation from exposure to nitro musks that are frequently used as fragrance ingredients in formulations of personal care products. Hemoglobin adducts serve as biomarkers of exposure of the sentinel species as we have shown in previous studies of hemoglobin adducts formed in trout and environmental carp exposed to musk xylene (MX) and musk ketone (MK). Gas chromatography-electron capture negative ion chemical ionization-mass spectrometry (GC-NICI-MS) employing selected ion monitoring is used to measure 4-amino-MX (4-AMX), 2-amino-MX (2-AMX), and 2-amino-MK (2-AMK) released by alkaline hydrolysis from the sulfinamide adducts of hemoglobin. Dose-response and toxicokinetics were investigated using this sensitive method for analysis of these metabolites. In the dose-response investigation, the concentrations of 4-AMX and 2-2AMX are observed to pass through a maximum at 0.10 mg/g. In the case of 2-AMK, the adduct concentration is almost the same at dosages in the range of 0.030 to 0.10 mg/g. For toxicokinetics, the concentration of the metabolites in the Hb reaches a maximum in the 3-day sample after administration of MX or MK. Further elimination of the metabolites exhibited kinetics with a presumed exponential decay and a half-life estimated to be 1-2 days. This suggests that a robust mechanism of elimination of the adducts exists in fish erythrocytes apparently analogous to that observed in mammals.

Two sick fish were observed to yield from 5 to 24 times the amount of adducts of similarly exposed fish, suggesting that this elimination mechanism may have been impaired or lacking in susceptible individual fish. It appears that adducts are destroyed in times far shorter than the expected life spans of the erythrocytes. This finding may have implications for the use of Hb biomarkers as integrative measures of exposure in some contexts. Additional conclusions from these preliminary data include the additive burden of exposure to multiple compounds and the increased susceptibility and direct observation of metabolic differences of individual members of the species completely independent of habitat and feeding habit variations.
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Citation:Mottaleb, M. A., W. C. Brumley, and G. W. Sovocool. Nitro Musk Adducts of Rainbow Trout Hemoglobin: Dose-Response and Toxicokinetics Determination By Gc-Nici-MS for a Sentinel Species. American Biotechnology Laboratory. International Scientific Communications, Inc., Shelton, CT, 23(7):26-29, (2005).
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Contact: Chris Siebert - (702) 798-2234 or siebert.christopher@epa.gov
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Division: Environmental Sciences Division
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Branch: Environmental Chemistry Branch
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Product Type: Journal
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Published: 06/24/2005
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Bullet Item Nitro Musk Adducts of Rainbow Trout Hemoglobin: Dose-Response and Toxicokinetics Determination By Gc-Nici-MS for a Sentinel Species
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