Abstract
The sensitivities of cytochrome P450 (EC 1.14.14.1)-dependent benzyloxy- and ethoxyphenoxazone dealkylase (BzOPh'ase and EtOPh'ase, respectively) activities towards a series of aliphatic hydrocarbons were measured in the microsomal fraction of lung obtained from β-naphthoflavone-treated rats. The unsubstituted hydrocarbons were straight-chain (n-hexane through n-undecane) and branch-chain (eight carbons). The substituted compounds were alcohols and ketones of hexane and octane. The data are expressed as I50 values, i.e. the hydrocarbon concentration required to cause 50% decrease in the rate of enzymecatalyzed product (resorufin) formation. The unsubstituted aliphatic hydrocarbons exhibited I50 values towards BzOPh'ase from 0.76 μM (2,5-dimethylhexane) to 8.8 μM (n-hexane). The lung EtOPh'ase activity was insensitive to-wards the tested unsubstituted aliphatic hydrocarbons. When the alcohols and ketones of hexane and octane were tested against lung BzOPh'ase activity, I50 values ranged from 16 μM (1-octanol) to 4.8 mM (2,5-hexanedione). Lung EtOPh'ase activity exhibited some sensitivity towards the alcohols and ketones, and I50 values ranged from 0.52 mM (4-octanol) to 40.5 mM (2-hexanol). The data show rat lung BzOPh'ase and EtOPh'ase activites are differentially sensitive towards the selected unsubstituted aliphatic hydrocarbons and corresponding alcohols and ketones. The difference in sensitivities may reflect different requirements for an adventitious interaction between a hydrocarbon and enzyme active site.
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References
Baron J, Kawabata TT (1983) Intratissue distribution of activating and detoxicating enzymes. In: Caldwell J, Jakoby WB (eds), Biological basis of detoxication. Academic Press, NY, pp 105–136
Bingham E, Falk H (1969) Environmental carcinogens: the modifying effect of carcinogens on the threshold response. Arch environ. Health 19: 779–783
Bingham E, Warshawsky D, Niemeier RW (1978) Metabolism of benzo[a]pyrene in the isolated perfused rabbit lung following N-dodecane inhalation. In: Alaga TJ, Sivak A, Boutwell RK (eds) Carcinogens. Raven Press NY, pp 509–516
Burke MD, Prough RA, Mayer RT (1977) Characteristics of microsomal cytochrome P-448-mediated reaction: ethoxyresorufin O-deethylation. Drug Metab Dispos 5: 1–8
Bus JS (1985) Alkanes. In: Anders MW (ed.) Bioactivation of foreign compounds. Academic Press, NY, pp 111–120
Clayton GD, Clayton FE (1982) Patty's industrial hygiene and toxicology, 3rd edn. John Wiley and Sons, NY, Vols. 2A, 2B, 2C
Dahl AR, Damon EG, Mauderly JL, Rothenberg SJ, Seiler FA, McClellan RO (1988) Uptake of 19 hydrocarbon vapors inhaled by F344 rats. Fundam Appl Toxicol 10: 262–269
Danner-Rabovsky J, Groseclose RD (1982) Stability of rat lung and liver microsomal cytochrome P450 enzyme activities to storage: purified microsomal fraction, postmitochondrial fraction and whole tissue. J Toxicol Environ Health 10: 601–611
Diamond JM, Katz Y (1974) Interpretation of nonelectrolyde partition coefficients between dimyristoyl lecithin in water. J Membr Biol 17: 121–154
Frommer U, Ulrich V, Staudinger H, Orrenius S (1972) The monooxygenation of n-heptane by rat liver microsomes. Biochim Biophys Acta 280: 487–494
Ichihara K, Kusunose E, Kusunose M (1969) Microsomal hydroxylation of heptane. Biochim Biophys Acta 176: 713–719
Keller GM, Turner CR, Jefcoate CR (1982) Kinetic determinants of benzo[a]pyrene metabolism to dihydrodiol epoxides by 3-methylcholanthrene-induced rat liver microsomes. Mol Pharmacol 22: 451–458
Krainer AG, Weiner LV, Alferyer IS, Mikhalin NV (1988) Localization of the active center of microsomal cytochrome P450. Biochem Biophys Res Commun 150: 426–435
MacFarland HN, Ulrich CE, Holdsworth CE, Kitchen DN, Halliwell WH, Blum SC (1984) A chronic inhalation study with unleaded gasoline vapor. J Amer Coll Toxicol 3: 231–248
McNamara BC, Jefcoate CR (1988) Synergistic stimulation of pregnenolone synthesis in rat adrenal mitochondria by n-hexane and cardiolipin. Arch Biochem Biophys 260: 780–788
Merck Index, 9th edn (1976) Merck & Co. Inc. NJ
Patty F, Irish D (1963) Industrial hygiene and toxicology, 2nd ed. Interscience Publishers, NY, Vol. 2
Perbellini L, Brugnone F, Caretta D, Maranelli G (1985) Partition coefficients of some industrial aliphatic hydrocarbons (C5–C7) in blood and human tissues. Br J Indust Med 42: 162–167
Plaa GL, Ayotte P (1985) Taurolithocholate-induced cholestasis: potentiation by methyl isobutyl ketone and methyl-n-butyl ketone in rats. Toxicol Appl Pharmacol 80: 225–234
Pope JM, Walker LW, Dubro D (1984) On the ordering of N-alkanes and n-alcohol solutes in phospholipid bilayer model membrane system. Chem Phys Lipids 35: 259–277
Prough RA, Burke MD, Mayers RT (1978) Direct fluorometric methods for measuring mixed-function oxidase activity. Meth Enzymol 52C: 372–377
Rabovsky J, Judy DJ (1987) Cytochrome P450-dependent alkoxyphenoxazone dealkylase activities in lung microsomes from untreated and β-naphthoflavone-treated rats: effect of in vitro inhibitors. Res Commun Chem Pathol Pharmacol 57: 375–388
Rabovsky J, Marion KJ, Resnick H (1985) Hydrocarbon solvents: effect on calcium mediated events in liposomes. Chem Phys Lipids 37: 13–18
Rabovsky J, Judy DJ, Pailes WH (1986) In vitro effects of straight-chain alkanes (n-hexane through n-dodecane) on rat liver and lung cytochrome P-450. J Toxicol Environ Health 18: 409–421
Sice J (1966) Tumor promoting activities of n-alkanes and l-alkanols. Toxicol Appl Pharmacol 9: 70–74
Toftgard R, Nilsen OG (1982) Effects of xylene and xylene isomers on cytochrome P-450 and in vitro enzymatic activities in rat liver, kidney and lung. Toxicology 23: 197–212
Toftgard R, Haaparanta T, Eng L, Halpert J (1986) Rat lung and liver microsomal cytochrome P-450 isozymes involved in the hydroxylation of n-hexane. Biochem Pharmacol 35: 3733–3738
Van Duuren BL, Goldschmidt BM (1976) Cocarcinogenic and tumor promoting agents in tobacco carcinogens. J Natl Cancer Inst 56: 1237–1242
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Rabovsky, J., Judy, D.J. The in vitro effects of alkanes, alcohols, and ketones on rat lung cytochrome P450-dependent alkoxyphenoxazone dealkylase activities. Arch Toxicol 63, 13–17 (1989). https://doi.org/10.1007/BF00334627
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DOI: https://doi.org/10.1007/BF00334627