Metabolism of inhalants

Andersen ME, Gargas ML, Jones RA, et al. 1980. Determination of the kinetic constants for metabolism of inhaled toxicants in vivo using gas uptake measurements. Toxicol Appl Pharmacol 54 100-116. 

Feingold A, Holaday DA. 1977. The pharmacokinetics of metabolism of inhalation anaesthetics. BrJ Anaesth 49 155-162. 

Hobara T, Kobayashi H, Kawamoto T, et al. 1986. Extrahepatic organs metabolism of inhaled trichloroethylene. Toxicology 41 289-303. 

The following physical, chemical, and biological factors related to the metabolism of inhaled and ingested radiocerium are recommended for establishing radiation protection guidelines ... 

The time-course of the metabolism of inhaled n-hexane in a group of 19 volunteers has been estimated by determining serum 2,5-hexanedione during and after a 15.5-minute exposure to 60 ppm n-hexane (van Engelen et al. 1997). The time to reach the peak concentration varied from 16.2 to 19.8 minutes after the... 

Exposure to other chemicals can influence the metabolism of -hexane. The effect of oral pretreatment with methyl ethyl ketone (MEK) on the metabolism of inhaled -hexane was investigated in male Fischer 344 rats (Robertson et al. 1989). Groups of 2-4 rats were given MEK (1.87 mL/kg, approximately 1,500 mg/kg) by gavage for 4 days prior to a single 6-hour inhalation exposure to w-hexane (1,000 ppm). Animals were sacrificed at 0, 1, 2, 4, 6, 8, and 18 hours after exposure ended, and samples of blood, liver, testis, and sciatic nerve were obtained and analyzed for -hexane, MEK, and their metabolites. Significant increases in the levels of the neurotoxic metabolite 2,5-hexanedione and 2,5-dimethylfuran (derived from 2,5-hexanedione) were found in blood and sciatic nerve of rats pretreated with MEK. Levels of 2,5-hexanedione in blood were approximately 10-fold higher than control immediately after -hexane exposure in rats and fell rapidly to approximately 2-fold after 6 hours. In sciatic nerve, increases in 2,5-hexanedione were approximately 6-fold at 2 hours and 3-fold at 4 hours. Similar patterns were found with 2,5-dimethylfuran. 2,5-Hexanedione was not detected in the testis of non-pretreated rats levels were measurable but very low in pretreated rats (0.3-0.6 g/g compared to... 

Gargas ML, Andersen ME. 1982. Metabolism of inhaled brominated hydrocarbons Validation of gas uptake results by determination of a stable metabolite. Toxicol AppI Pharmacol 66 55-68. 

Gargas Ml, et al Metabolism of inhaled dihalomethanes in vivo differentiation of kinetic constants for two independent pathways. Toxicol ApplPharmacol 9i2-2 -221i, 1986... 

Engstrom, K.M. (1984b) Metabolism of inhaled ethylbenzene in rats. Scand. J. Work environ. Health, 10, 83-87... 

The metabolism of inhaled [ CJdichloroacetylene has been studied in male Wistar... 

Droz, P.O., and J.G. Fernandez. 1977. Effect of physical workload on retention and metabolism of inhaled organic solvents. A comparative theoretical approach and its applications with regards to exposure monitoring. Int. Arch. Occup. Environ. Health. 38(4) 231-246. 

Morgan, A., Morgan, D.J. Arkell, G.M. (1966) A study of the retention and subsequent metabolism of inhaled methyl iodide. In Inhaled Particles and Vapours II, ed. W.H. Walton, pp. 309-21. Oxford Pergamon. 

Metabolism of inhaled anesthetics usually begins with oxidation and is carried out by cytochrome P-450 enzymes located in the microsomes of fhe hver and the kidneys [30, 31]. Under certain circumstances, some agents, such as halothane, might also undergo reduction. In addition to their primary metabolism, some anesthetics, sevoflurane for instance, also undergo phase II conjugation reactions prior to excretion. 

Urinary phenol, cresols, /7-nitrophenol, and /7-aminophe-nol are biological indicators of human exposure to aromatic hydrocarbons. Fig. 7 illustrates the scheme of phase 1 and phase 2 metabolism of inhaled benzene and toluene vapors, while Fig. 8 shows the metabolism of inhaled xylene and ethyl benzene vapors. 

Fig. 7 Scheme of phase 1 and phase 2 metabolism of inhaled benzene and toluene vapors. 

Clarkson TW. 1978. The metabolism of inhaled mercury vapor in animals and man. Preprints of papers presented at the 176th National Meeting of the American Chemical Society, Division of Environmental Chemistry, September, Miami Beach, FI. Washington, DC American Chemical Society, 274-275. 

Nolan RJ, Freshour NL, Rick DL. 1984. Kinetics and metabolism of inhaled methyl chloroform (1,1,1-trichloroethane) in male volunteers. Fundam Appl Toxicol 4 654-662. 

Medinsky MA, Cuddihy RG, Griffith WC, et al. 1981a. A simulation model describing the metabolism of inhaled and ingested selenium compounds. Toxicol Appl Pharmacol 59 54-63. 

McKenna MJ, DiStefano V. 1977a. Carbon disulfide I. The metabolism of inhaled carbon disulfide in the rat. J Pharmacol Exp Ther 202 245-252. 

However, Gehring et al. were able to utilize dose response data obtained above the pharmacokinetic threshold by determining the pharmacokinetic parameters describing the saturable metabolism of inhaled VC in rats (S), With knowledge of the Vm and values for the metabolic transformation of VC in rats, it was possible to index the observed response to the internal dose level of the toxic entity (the amount of VC metabolized), rather than to the exposure level. 

The major pathways of metabolism of inhaled formaldehyde are oxidation to formate and incorporation into biological macromolecules via tetra-hydrofolate-dependent one-carbon biosynthetic pathways (Huennekens and Osborne 1959, Koi-VUSALO et al. 1982). The most important pathway for oxidation appears to be that catalysed by formaldehyde dehydrogenase (EC 1.2.1.1), an enzyme that requires both glutathione and NAD as cofactors. UOTiLA and Koivusalo (1974) showed that the true substrate is the hemithioacetal adduct of formaldehyde and glutathione and the product formed is the thiol ester of formic acid, S-formylglutathione. 

Hayes AD, Rothstein A (1962) The metabolism of inhaled mercury vapor in the rat studied by isotope techniques. J. Pharmacol. 138 1 Hursh JB, Clarkson TW, Cherian MG, Vostal JV, Mallie RV (1976) Clearance of mercury ( Hg, Hg) vapor inhaled by human siibjects. Arch. Environ. Health 31 ... 

Morgan, A., Morgan, D.J., Evans, J.C. and Lister, B.A.J. (1967). Studies on the retention and metabolism of inhaled methyl iodide II Metabolism of methyl iodide, Health Phys. 13,1067. 

Pulmonary epithelial cells have been extensively characterized as the producers of pulmonary surfactant lipid and protein species and in their role in the repair of epithelial damage through increased cell proliferation and subsequent differentiation. It is also clear that a subpopulation of the respiratory epithelium is capable of uptake, accumulation, and metabolism of inhaled and systemic lipophilic substances (89). 

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