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Title: Benzene toxicity: emphasis on cytosolic dihydrodiol dehydrogenases

Abstract

Blood dyscrasias such as leukopenia and anemia have been clearly identified as consequences of chronic benzene exposure. The metabolites, phenol, catechol, and hydroquinone produced inhibition of /sup 59/Fe uptake in mice which followed the same time course as that produced by benzene. The inhibitor of benzene oxidation, 3-amino-1,2,4-triazole, mitigated the inhibitory effects of benzene and phenol only. These data support the contention that benzene toxicity is mediated by a metabolite and suggest that the toxicity of phenol is a consequence of its metabolism to hydroquinone and that the route of metabolism to catechol may also contribute to the production of toxic metabolite(s). The properties of mouse liver cytosolic dihydrodiol dehydrogenases were examined. These enzymes catalyze the NADP/sup +/-dependent oxidation of trans-1,2-dihydro-1,2-dihydroxybenzene (BDD) to catechol, a possible toxic metabolite of benzene produced via this metabolic route. Four distinct dihydrodiol dehydrogenases (DD1, DD2, DD3, and DD4) were purified to apparent homogeneity as judged by SDS polyacrylamide gel electrophoresis and isoelectric focusing. DD1 appeared to be identical to the major ketone reductase and 17..beta..-hydroxysteroid dehydrogenase activity in the liver. DD2 exhibited aldehyde reductase activity. DD3 and DD4 oxidized 17..beta..-hydroxysteroids, but no carbonyl reductase activity was detected. These relationships between BDD dehydrogenases and carbonylmore » reductase and/or 17..beta..-hydroxysteroid dehydrogenase activities were supported by several lines of evidence.« less

Authors:
Publication Date:
OSTI Identifier:
5741131
Resource Type:
Thesis/Dissertation
Resource Relation:
Other Information: Thesis (Ph. D.)
Country of Publication:
United States
Language:
English
Subject:
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.; BENZENE; METABOLISM; TOXICITY; OXIDOREDUCTASES; ENZYME ACTIVITY; STEROIDS; LIVER; MICE; ANIMALS; AROMATICS; BODY; DIGESTIVE SYSTEM; ENZYMES; GLANDS; HYDROCARBONS; MAMMALS; ORGANIC COMPOUNDS; ORGANS; RODENTS; VERTEBRATES 560305* -- Chemicals Metabolism & Toxicology-- Vertebrates-- (-1987)

Citation Formats

Bolcsak, L.E.. Benzene toxicity: emphasis on cytosolic dihydrodiol dehydrogenases. United States: N. p., 1982. Web.
Bolcsak, L.E.. Benzene toxicity: emphasis on cytosolic dihydrodiol dehydrogenases. United States.
Bolcsak, L.E.. 1982. "Benzene toxicity: emphasis on cytosolic dihydrodiol dehydrogenases". United States. doi:.
@article{osti_5741131,
title = {Benzene toxicity: emphasis on cytosolic dihydrodiol dehydrogenases},
author = {Bolcsak, L.E.},
abstractNote = {Blood dyscrasias such as leukopenia and anemia have been clearly identified as consequences of chronic benzene exposure. The metabolites, phenol, catechol, and hydroquinone produced inhibition of /sup 59/Fe uptake in mice which followed the same time course as that produced by benzene. The inhibitor of benzene oxidation, 3-amino-1,2,4-triazole, mitigated the inhibitory effects of benzene and phenol only. These data support the contention that benzene toxicity is mediated by a metabolite and suggest that the toxicity of phenol is a consequence of its metabolism to hydroquinone and that the route of metabolism to catechol may also contribute to the production of toxic metabolite(s). The properties of mouse liver cytosolic dihydrodiol dehydrogenases were examined. These enzymes catalyze the NADP/sup +/-dependent oxidation of trans-1,2-dihydro-1,2-dihydroxybenzene (BDD) to catechol, a possible toxic metabolite of benzene produced via this metabolic route. Four distinct dihydrodiol dehydrogenases (DD1, DD2, DD3, and DD4) were purified to apparent homogeneity as judged by SDS polyacrylamide gel electrophoresis and isoelectric focusing. DD1 appeared to be identical to the major ketone reductase and 17..beta..-hydroxysteroid dehydrogenase activity in the liver. DD2 exhibited aldehyde reductase activity. DD3 and DD4 oxidized 17..beta..-hydroxysteroids, but no carbonyl reductase activity was detected. These relationships between BDD dehydrogenases and carbonyl reductase and/or 17..beta..-hydroxysteroid dehydrogenase activities were supported by several lines of evidence.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1982,
month = 1
}

Thesis/Dissertation:
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  • This study was conducted by either literature review or actual field survey. Results are summarized as follows: (1) long-term occupational exposure of workers to benzene vapor at levels of 3 to 7 ppM, 2 to 3 ppM and 1.6 ppM may result in a decreased level of leucocyte alkaline phosphates, an increased incidence of chromosome aberrations and an increased level of ALA in erythrocytes, respectively; (2) benzene is capable of causing fetotoxic effects in animals at levels as low as 10 ppM by volume; (3) exposure of animals to or less than 1 ppM benzene vapor may result in leucopenia,more » an inverse ratio of muscle antagonist chronaxy and a decreased level of ascorbic acid in fetus's and mother's liver as well as whole embryo; (4) benzene is causally associated with the increased incidence of pancytopenia, including unicytopenia, bicytopenia and aplastic anemia, and chromosome aberrations in occupational exposure population, and at best benzene must also be considered as a leukemogen; (5) since it can be emitted into the atmosphere from both man-made and natural sources, benzene in some concentrations is presented everywhere in the various compartments of the environment; (6) the findings of the emission of benzene from certain natural sources indicate that reducing benzene to a zero-level of exposure is theoretically impossible; (7) the annual average of benzene concentration detected in the Houston ambient air is 2.50 ppB, which is about 2.4 times higher than the nation-wide annual average exposure level and may have some health implications to the general public; and (8) in the Houston area, stationary sources are more important than mobile sources in contributing to benzene in the ambient air.« less
  • Exposure to benzene, is associated with numerous blood disorders including pancytopenia and leukemia. Despite extensive research, the mechanism by which benzene exerts toxicity is unknown. Since benzene toxicity occurs in the bone marrow, an organ with a high capacity for free radical generation, the objective of this dissertation was to investigate the potential role of free radicals, free radical generating systems and quinone formation in benzene's myelotoxicity.
  • Carcinogenic activation of polycyclic aromatic hydrocarbons by microsomal monoxygenases proceeds through trans-dihydrodiol metabolites to diol-epoxide ultimate carcinogens. This thesis directly investigated the role of dihydrodiol dehydrogenase, a cytosolic NAD(P)-linked oxidoreductase, in the detoxification of polycyclic aromatic trans-dihydrodiols. A wide variety of non-K-region trans-dihydrodiols were synthesized and shown to be substrates for the homogeneous rat liver dehydrogenase, including several potent proximate carcinogens derived from 7,12-dimethylbenz(a)anthracene, 5-methylchrysene, and benzo(a)pyrene. Since microsomal activation of polycyclic aromatic hydrocarbons is highly stereospecific, the stereochemical course of enzymatic trans-dihydrodiol oxidation was monitored using circular dichroism spectropolarimetry. The major product formed from the dehydrogenase-catalyzed oxidation of themore » trans-1,2-dihydrodiol of naphthalene was characterized using UV, IR, NMR, and mass spectroscopy, and appears to be 4-hydroxy-1,2-naphthoquinone. Mass spectral analysis suggests that an analogous hydroxylated o-quinone is formed as the major product of benzo(a)pyrene-7,8-dihydrodiol oxidation. Enzymatic oxidation of trans-dihydrodiols was shown to be potently inhibited by all of the major classes of the nonsteroidal antiinflammatory drugs. Enhancement of trans-dihydrodiol proximate carcinogen oxidation may protect against possible adverse effects of the aspirin-like drugs, and help maintain the balance between activation and detoxification of polycyclic aromatic hydrocarbons.« less
  • The purpose of this study was to investigate the effects of adrenalectomy on the control and ..cap alpha..-adrenergic regulation of the concentration of cytosolic free calcium (Ca/sub i/) in hepatocytes. In hepatocytes isolated from adrenalectomized (adx) and sham-operated male rats 7-1 days after surgery, Ca/sub i/ at rest and in response to epinephrine (EPI) was measured with the calcium-sensitive photoprotein aequorin, /sup 45/Ca efflux was measured, and Ca/sup 2 +/ release from intracellular stores in response to inositol triphosphate (IP/sub 3/) was measured in saponin-permeabilized cells. Liver calmodulin content was also assayed by radioimmunoassay. It was found in adx ratsmore » that the resting Ca/sub i/ was elevated, the rise in Ca/sub i/ during EPI stimulation was reduced at physiological EPI concentrations, and the rise in calcium efflux evoked by EPI was reduced. Furthermore, the slope of the relationship between Ca/sub i/ and calcium efflux was reduced 60% in adx. Adx did not alter the characteristics of Ca/sup 2 +/ release from intracellular calcium pools in response to IP/sub 3/ in permeabilized cells. Finally, the liver calmodulin contents were not significantly different between the 2 groups.« less
  • In order to investigate the basis for the MOD-1 null mutation, a {lambda}gt 11 cDNA library was constructed using mRNA from the livers of induced MOD-1 null mice as a template. A recombinant phage with a 2kb insert was isolated by screening with wild type malic enzyme cDNA probes. The subcloned insert exhibited an atypical (non-wild type) restriction pattern and was subjected to sequence analysis. MOD-1 null malic enzyme cDNA contains an internal, tandemly-duplicated sequence that corresponds to nucleotides 1027-1548 in the coding region of wild type murine malic enzyme cDNA. An open reading frame is retained throughout the duplicatedmore » sequences. The discovery of a 522 nucleotide, in-frame duplication accounts for the increased size of MOD-1 null malic enzyme mRNAs. Western immunoblot analysis disclosed that MOD-1 null liver cytosol contains an 82 kDa protein that is recognized by anti malic enzyme antibodies. Under stringent conditions, an anti-sense {sup 32}P-oligonucleotide that spans the abnormal junction between the reiterated sequences hybridized with the 2.5 and 3.6 kb MOD-1 null malic enzyme mRNAs, but failed to form stable complexes with wild type malic enzyme mRNAs.« less