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Basics of toxicology
Published in Chris Winder, Neill Stacey, Occupational Toxicology, 2004
Another common phase II reaction is via the enzyme glutathione S-transferase, which is actually a family of enzymes responsible for the eventual formation of mercapturic acid or thioether metabolites. These have been determined in urine in biological monitoring for exposure to some chemicals. As the name implies the cofactor for the enzyme is the tripeptide, reduced glutathione. This is a widely studied reactant in the detoxification of a variety of chemicals. If its supply is limited increased toxicity may be observed.
Behavior of PAH in the Organism
Published in Grimmer Gemot, Dr. Chem., Environmental Carcinogens: Polycyclic Aromatic Hydrocarbons, 1983
In rat kidneys the glutathione compound of naphthalene is enzymatically decomposed by elimination of glutamic acid to form the cysteinyl-glycine compound which is then metabolized to the cysteine compound by cleavage of the glycine. After acetylation this cysteine compound is excreted as mercapturic acid.
Polycyclic aromatic hydrocarbons (PAHs): Updated aspects of their determination, kinetics in the human body, and toxicity
Published in Journal of Toxicology and Environmental Health, Part B, 2023
Fernando Barbosa, Bruno A. Rocha, Marília C. O. Souza, Mariana Z. Bocato, Lara F. Azevedo, Joseph A. Adeyemi, Anthony Santana, Andres D. Campiglia
PAHs are hydroxylated and excreted in urine and feces (Bendadani et al. 2016; Chien and Yeh 2012). The absorbed PAHs are acted upon by different metabolizing enzymes (mainly of the cytochrome P450 family) to produce reactive metabolites such as epoxides, phenols, and dihydrodiols. These metabolites bind to cellular biomolecules including DNA and proteins, which may result in cancer, developmental aberrations, and cardiovascular dysfunction (Gao et al. 2018). PAH molecules are activated by binding to the aryl hydrocarbon receptor (AhR), which increases production of cytochrome enzymes (Nebert et al. 2004). The metabolites glucuronide- and sulfate conjugates are excreted in the bile and urine. In contrast, glutathione conjugates are metabolized to mercapturic acid in kidneys and excreted in urine (ATSDR (Agency for Toxic Substances and Disease Registry) 1995).
Electronic cigarette-generated aldehydes: The contribution of e-liquid components to their formation and the use of urinary aldehyde metabolites as biomarkers of exposure
Published in Aerosol Science and Technology, 2018
Daniel J. Conklin, Mumiye A. Ogunwale, Yizheng Chen, Whitney S. Theis, Michael H. Nantz, Xiao-An Fu, Lung-Chi Chen, Daniel W. Riggs, Pawel Lorkiewicz, Aruni Bhatnagar, Sanjay Srivastava
Propylene glycol (PG; >99.5%) and vegetable glycerin (VG; 99.5%), as well as LC-MS grade methanol, were purchased from Sigma-Aldrich (Milwaukee, WI). Several brands of e-cigs and e-liquids were purchased locally or online: Set I (blu®: Classic Tobacco, CT; Magnificent Menthol, MM; Vivid Vanilla, VV; Cherry Crush, CC) and Set II (Halo®: Menthol, Mocha Café, Southern Ice). As labeled by the vendor, Set I e-cartridges contained 13–16 mg nicotine, whereas Set II e-liquids contained 6 mg/mL nicotine. Ultra-pure water was used in making solutions (Milli-Q system; Millipore Corporation; Bedford, MA). KY reference cigarettes, 3R4F, were purchased from the Center for Tobacco Reference Products (Univ. Kentucky; Lexington, KY). Isotopically-labeled standards (IS) for UPLC-MS/MS analysis: d3-nicotine, d3-cotinine, d3-3-hydroxycotinine (d3-3HC), d3-3-hydroxypropyl mercapturic acid (d3-3HPMA), and d3-N-Acetyl-S-(3-hydroxypropyl-1-methyl)-L-cysteine (d3-HPMMA) were purchased from Toronto Research Chemicals (Toronto, Canada).
Occupational exposure to aflatoxins and health outcomes: a review
Published in Journal of Environmental Science and Health, Part C, 2019
Ruth Nabwire Wangia, Lili Tang, Jia-Sheng Wang
In Phase II, the reactive epoxide undergoes detoxification via two different pathways. One route is glutathione S-transferase [GST]-mediated pathway where the epoxide is conjugated by glutathione (GSH) to form AFB1 glutathione conjugate, which is excreted in urine as mercapturic acid.48 Alternatively, non-enzymatic processes hydrolyze the epoxides to 8, 9-dihydrodiol, which undergoes base-catalyzed ring opening to dialdehyde phenolate ion. The AFB1 aldehyde reductase (AFAR) catalyzes the conversion of the dialdehyde phenolate ion to dialcohol that is excreted in urine.48