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Simultaneous quantification of multiple urinary naphthalene metabolites by liquid chromatography tandem mass spectrometry.

Ayala DC, Morin D, Buckpitt AR - PLoS ONE (2015)

Bottom Line: Subsequent biotransformation results in urinary elimination of several conjugated metabolites.The method is robust and directly measures several major naphthalene metabolites including those derived from glutathione conjugation of naphthalene epoxide.The assays do not require enzymatic deconjugation, extraction or derivatization thus simplifying sample work up.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biosciences, School of Veterinary Medicine, University of California Davis, Davis, CA 95616, United States of America; University of California Davis, Forensic Science, Graduate Program, 1909 Galileo Ct., Suite B, Davis, CA 95618, United States of America.

ABSTRACT
Naphthalene is an environmental toxicant to which humans are exposed. Naphthalene causes dose-dependent cytotoxicity to murine airway epithelial cells but a link between exposure and human pulmonary disease has not been established. Naphthalene toxicity in rodents depends on P450 metabolism. Subsequent biotransformation results in urinary elimination of several conjugated metabolites. Glucuronide and sulfate conjugates of naphthols have been used as markers of naphthalene exposure but, as the current studies demonstrate, these assays provide a limited view of the range of metabolites generated from the parent hydrocarbon. Here, we present a liquid chromatography tandem mass spectrometry method for measurement of the glucuronide and sulfate conjugates of 1-naphthol as well as the mercapturic acids and N-acetyl glutathione conjugates from naphthalene epoxide. Standard curves were linear over 2 log orders. On column detection limits varied from 0.91 to 3.4 ng; limits of quantitation from 1.8 to 6.4 ng. The accuracy of measurement of spiked urine standards was -13.1 to + 5.2% of target and intra-day and inter-day variability averaged 7.2 (± 4.5) and 6.8 (± 5.0) %, respectively. Application of the method to urine collected from mice exposed to naphthalene at 15 ppm (4 hrs) showed that glutathione-derived metabolites accounted for 60-70% of the total measured metabolites and sulfate and glucuronide conjugates were eliminated in equal amounts. The method is robust and directly measures several major naphthalene metabolites including those derived from glutathione conjugation of naphthalene epoxide. The assays do not require enzymatic deconjugation, extraction or derivatization thus simplifying sample work up.

No MeSH data available.


Related in: MedlinePlus

Naphthalene metabolite-specific percentages of total quantified metabolite during repeated naphthalene exposure treatments (15 ppm x 4hrs daily) via inhalation.
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pone.0121937.g004: Naphthalene metabolite-specific percentages of total quantified metabolite during repeated naphthalene exposure treatments (15 ppm x 4hrs daily) via inhalation.

Mentions: The entire experimental cohort (2 groups of 3 mice) produced daily urine samples which all contained detectable levels of all four targeted naphthalene metabolites. All control animal urine samples had levels below the method LOD. Fig 3A shows an overall increase in glutathione-derived metabolite (mercapturic acid, N-acetyl GSH) excretion over the entire exposure experiment. The mercapturic acid ranged from 139.5–263.5 nmoles excreted/24 hrs and represented, on average, greater than 60% of the total amount of quantified metabolites in each daily urine sample (range: 57.2–67.2%) (Fig 4). Over the 7 days, N-acetyl GSH steadily increased from 2.1 to 12.3 nmoles and represented an average 1–3% (range: 0.9–3.3%) contribution of total metabolite amount excreted (Fig 4).


Simultaneous quantification of multiple urinary naphthalene metabolites by liquid chromatography tandem mass spectrometry.

Ayala DC, Morin D, Buckpitt AR - PLoS ONE (2015)

Naphthalene metabolite-specific percentages of total quantified metabolite during repeated naphthalene exposure treatments (15 ppm x 4hrs daily) via inhalation.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390350&req=5

pone.0121937.g004: Naphthalene metabolite-specific percentages of total quantified metabolite during repeated naphthalene exposure treatments (15 ppm x 4hrs daily) via inhalation.
Mentions: The entire experimental cohort (2 groups of 3 mice) produced daily urine samples which all contained detectable levels of all four targeted naphthalene metabolites. All control animal urine samples had levels below the method LOD. Fig 3A shows an overall increase in glutathione-derived metabolite (mercapturic acid, N-acetyl GSH) excretion over the entire exposure experiment. The mercapturic acid ranged from 139.5–263.5 nmoles excreted/24 hrs and represented, on average, greater than 60% of the total amount of quantified metabolites in each daily urine sample (range: 57.2–67.2%) (Fig 4). Over the 7 days, N-acetyl GSH steadily increased from 2.1 to 12.3 nmoles and represented an average 1–3% (range: 0.9–3.3%) contribution of total metabolite amount excreted (Fig 4).

Bottom Line: Subsequent biotransformation results in urinary elimination of several conjugated metabolites.The method is robust and directly measures several major naphthalene metabolites including those derived from glutathione conjugation of naphthalene epoxide.The assays do not require enzymatic deconjugation, extraction or derivatization thus simplifying sample work up.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biosciences, School of Veterinary Medicine, University of California Davis, Davis, CA 95616, United States of America; University of California Davis, Forensic Science, Graduate Program, 1909 Galileo Ct., Suite B, Davis, CA 95618, United States of America.

ABSTRACT
Naphthalene is an environmental toxicant to which humans are exposed. Naphthalene causes dose-dependent cytotoxicity to murine airway epithelial cells but a link between exposure and human pulmonary disease has not been established. Naphthalene toxicity in rodents depends on P450 metabolism. Subsequent biotransformation results in urinary elimination of several conjugated metabolites. Glucuronide and sulfate conjugates of naphthols have been used as markers of naphthalene exposure but, as the current studies demonstrate, these assays provide a limited view of the range of metabolites generated from the parent hydrocarbon. Here, we present a liquid chromatography tandem mass spectrometry method for measurement of the glucuronide and sulfate conjugates of 1-naphthol as well as the mercapturic acids and N-acetyl glutathione conjugates from naphthalene epoxide. Standard curves were linear over 2 log orders. On column detection limits varied from 0.91 to 3.4 ng; limits of quantitation from 1.8 to 6.4 ng. The accuracy of measurement of spiked urine standards was -13.1 to + 5.2% of target and intra-day and inter-day variability averaged 7.2 (± 4.5) and 6.8 (± 5.0) %, respectively. Application of the method to urine collected from mice exposed to naphthalene at 15 ppm (4 hrs) showed that glutathione-derived metabolites accounted for 60-70% of the total measured metabolites and sulfate and glucuronide conjugates were eliminated in equal amounts. The method is robust and directly measures several major naphthalene metabolites including those derived from glutathione conjugation of naphthalene epoxide. The assays do not require enzymatic deconjugation, extraction or derivatization thus simplifying sample work up.

No MeSH data available.


Related in: MedlinePlus