Improved measurement of protein synthesis in human subjects using 2
H-phenylalanine isotopomers and gas chromatography/mass spectrometry

Background Sevoflurane undergoes Baralyme- or soda lime-catalyzed degradation in the anesthesia circuit to yield compound A (2-[fluoromethoxy]-1,1,3,3,3-pentafluroro-1-propene), which is nephrotoxic in rats and undergoes metabolism via the cysteine conjugate beta-lyase pathway in those animals. The objective of these experiments was to test the hypothesis that compound A undergoes beta-lyase-dependent metabolism in humans. Methods Human volunteers were anesthetized with sevoflurane (1.25 minimum alveolar concentration, 3%, 2 l/min, 8 h) and thereby exposed to compound A. Urine was collected at 24-h intervals for 72 h after anesthesia. Rats, which served as a positive control, were given compound A intraperitoneally, and urine was collected for 24 h afterward. Human and rat urine samples were analyzed by 19F nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry for the presence of compound A metabolites. Results Analysis of human and rat urine showed the presence of the compound A metabolites S-[2(fluoromethoxy)-1,1,3,3,3-pentafluoropropyl]-N-acetyl-L- cysteine, (E)- and (Z)-S-[2-(fluoromethoxy)-1,3,3,3-tetrafluoro-1-propenyl]-N-acetyl- L-cysteine, 2-(fluoromethoxy)-3,3,3-trifluoropropanoic acid, 3,3,3-trifluorolactic acid, and inorganic fluoride. The presence of 2-(fluoromethoxy)3,3,3-trifluoropropanoic acid and 3,3,3-trifluorolactic acid in human urine was confirmed by gas chromatography-mass spectrometry. Conclusions The formation of compound A-derived mercapturates shows that compound A undergoes glutathione S-conjugate formation. The identification of 2-(fluoromethoxy)-3,3,3-trifluoropropanoic acid and 3,3,3-trifluorolactic acid in the urine of humans anesthetized with sevoflurane shows that compound A undergoes beta-lyase-dependent metabolism. Metabolite formation was qualitatively similar in both human volunteers anesthetized with sevoflurane, and thereby exposed to compound A, and in rats given compound A, indicating that compound A is metabolized by the beta-lyase pathway in both species.

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Simultaneous Determination of Pyrethroid, Organophosphate and Carbamate Metabolites in Human Urine by Gas Chromatography–Mass Spectrometry (GCMS)

Applied Sciences ◽

10.3390/app9050879 ◽

2019 ◽

Vol 9 (5) ◽

pp. 879 ◽

Cited By ~ 2

Author(s):

Chien-Che Hung ◽

Sailent Simaremare ◽

Chia-Jung Hsieh ◽

Lih-Ming Yiin

Keyword(s):

Mass Spectrometry ◽

Gas Chromatography ◽

Simultaneous Determination ◽

Human Subjects ◽

Urinary Metabolites ◽

Gas Chromatography Mass Spectrometry ◽

Chromatography Mass Spectrometry ◽

Relative Standard ◽

Pyrethroid Metabolites

We have developed a rapid, sensitive, and reliable method for simultaneous determination of the urinary metabolites of common insecticides in a single analytical run using gas chromatography–mass spectrometry (GCMS). Thirteen metabolites, one originating from carbamate, six from organophosphates, and seven from pyrethroids, were selected for method validation. Samples at different concentrations (0.5–15 µg/L) were prepared by mixing working solutions containing the analytes with blank urine. After acid hydrolysis for 45 min at 90 °C, samples were processed with liquid–liquid extraction and derivatization by N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA) before analysis on GCMS. The limits of detection for all thirteen analytes were below 0.1 µg/L. The recovery rates, evaluated at two concentrations (1, 10 µg/L), were found to be 90.48%, on average. The precision of multiple analyses at three different concentrations (0.5, 5, 15 µg/L) within one day or between 10 days was evaluated, and the resultant relative standard deviations were 8.1% or under. We also applied this method to analyze genuine urine samples collected from 30 human subjects, and successfully detected all the metabolites, with detection frequencies more than 50% for pyrethroid metabolites. In summary, this method is not only as good as others in performance, but is advantageous in terms of cost effectiveness and multiplicity of analytes.

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Codeine Concentration in Hair after Oral Administration Is Dependent on Melanin Content

Clinical Chemistry ◽

10.1093/clinchem/45.9.1485 ◽

1999 ◽

Vol 45 (9) ◽

pp. 1485-1494 ◽

Cited By ~ 76

Author(s):

Robert Kronstrand ◽

Sophie Förstberg-Peterson ◽

Bertil KÅgedal ◽

Johan Ahlner ◽

Göran Larson

Keyword(s):

Mass Spectrometry ◽

Gas Chromatography ◽

Human Subjects ◽

Area Under The Curve ◽

Gas Chromatography Mass Spectrometry ◽

Melanin Content ◽

Exponential Relationship ◽

Chromatography Mass Spectrometry ◽

Hair Samples ◽

Drug Incorporation

Abstract Background: Analysis of drugs in hair has been used on a qualitative basis to estimate earlier exposure to drugs. Clinical applications are rare because of the lack of dose–response relationships in the studies performed to date, and questions remain regarding the mechanisms of drug incorporation into hair. Several human studies have shown differences in drug accumulation between pigmented and nonpigmented hair. However, the melanin concentration in hair was not determined and correlated to the amount of drug incorporated. Methods: Nine human subjects were given codeine as a single oral dose, and plasma codeine concentrations were determined for 24 h, using gas chromatography–mass spectrometry. Hair samples were obtained weekly for a month. Total melanin, eumelanin, and codeine were measured quantitatively in hair samples by spectrophotometry, HPLC, and gas chromatography–mass spectrometry, respectively. Results: There was an exponential relationship between codeine and melanin concentrations in hair, (r2 = 0.95 with total melanin and r2 = 0.83 with eumelanin). After normalizing the results by the area under the curve for codeine in plasma, we obtained r2 = 0.86 for codeine vs total melanin and r2 = 0.90 vs eumelanin. Conclusions: Our results stress the importance of melanin determination when measuring drugs in hair. We postulate that analysis of drug concentration in hair may be worthwhile in the monitoring of drug compliance if the results are normalized for melanin content.

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