Metabolism, toxicokinetics and hemoglobin adduct formation in rats following subacute and subchronic acrylamide dosing

D. S. Barber, J. R. Hunt, M. F. Ehrich, E. J. Lehning, Richard M. LoPachin

Research output: Contribution to journalArticle

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Abstract

Long-term, low-dose (subchronic) oral acrylamide (ACR) exposure produces peripheral nerve axon degeneration, whereas irreversible axon injury is not a component of short-term, higher dose (subacute) i.p. intoxication [Toxicol Appl Pharmacol 1998;151:211]. It is possible that this differential axonopathic expression is a product of exposure-dependent differences in ACR biotransformation and/or tissue distribution. Therefore, we determined the toxicokinetics and metabolism of A CR following subchronic oral (2.8 mM in drinking water for 34 days) or subacute i.p. (50 mg/kg per day for 11 days) administration to rats. Both dosing regimens produced moderate levels of behavioral neurotoxicity and, for each, ACR was rapidly absorbed from the site of administration and evenly distributed to tissues. Peak ACR plasma concentrations and tissue levels were directly related to corresponding daily dosing rates (20 or 50 mg/kg per day). During subchronic oral dosing a larger proportion (30%) of plasma ACR was converted to the epoxide metabolite glycidamide (GLY) than was observed following subacute i.p. intoxication (8%). This subchronic effect was not specifically related to changes in enzyme activities involved in GLY formation (cytochrome P450 2E1) or metabolism (epoxide hydrolases). Both ACR and GLY formed hemoglobin adducts during subacute and subchronic dosing, the absolute quantity of which did not change as a function of neurotoxicant exposure. Compared to subacute i.p. exposure, the subchronic schedule produced approximately 30% less ACR adducts but two-fold more GLY adducts. GLY has been considered to be an active ACR metabolite and might mediate axon degeneration during subchronic ACR administration. However, corresponding peak GLY plasma concentrations were relatively low and previous studies have shown that GLY is only a weak neurotoxicant. Our study did not reveal other toxicokinetic idiosyncrasies that might be a basis for subchronic induction of irreversible axon damage. Consequently the mechanism of axon degeneration does not appear to involve route- or rate-dependent differences in metabolism or disposition.

Original languageEnglish (US)
Pages (from-to)341-353
Number of pages13
JournalNeuroToxicology
Volume22
Issue number3
DOIs
StatePublished - 2001

Fingerprint

Acrylamide
Metabolism
Rats
Hemoglobins
Axons
Tissue
Metabolites
Plasmas
Epoxide Hydrolases
Toxicokinetics
Cytochrome P-450 CYP2E1
Nerve Degeneration
Epoxy Compounds
Enzyme activity
Tissue Distribution
Biotransformation
glycidamide
Peripheral Nerves
Drinking Water
Appointments and Schedules

Keywords

  • Adduct formation
  • Glycidamide
  • Neurotoxicant metabolism
  • Toxic axonopathy

ASJC Scopus subject areas

  • Cellular and Molecular Neuroscience
  • Neuroscience(all)
  • Toxicology

Cite this

Metabolism, toxicokinetics and hemoglobin adduct formation in rats following subacute and subchronic acrylamide dosing. / Barber, D. S.; Hunt, J. R.; Ehrich, M. F.; Lehning, E. J.; LoPachin, Richard M.

In: NeuroToxicology, Vol. 22, No. 3, 2001, p. 341-353.

Research output: Contribution to journalArticle

Barber, D. S. ; Hunt, J. R. ; Ehrich, M. F. ; Lehning, E. J. ; LoPachin, Richard M. / Metabolism, toxicokinetics and hemoglobin adduct formation in rats following subacute and subchronic acrylamide dosing. In: NeuroToxicology. 2001 ; Vol. 22, No. 3. pp. 341-353.
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AB - Long-term, low-dose (subchronic) oral acrylamide (ACR) exposure produces peripheral nerve axon degeneration, whereas irreversible axon injury is not a component of short-term, higher dose (subacute) i.p. intoxication [Toxicol Appl Pharmacol 1998;151:211]. It is possible that this differential axonopathic expression is a product of exposure-dependent differences in ACR biotransformation and/or tissue distribution. Therefore, we determined the toxicokinetics and metabolism of A CR following subchronic oral (2.8 mM in drinking water for 34 days) or subacute i.p. (50 mg/kg per day for 11 days) administration to rats. Both dosing regimens produced moderate levels of behavioral neurotoxicity and, for each, ACR was rapidly absorbed from the site of administration and evenly distributed to tissues. Peak ACR plasma concentrations and tissue levels were directly related to corresponding daily dosing rates (20 or 50 mg/kg per day). During subchronic oral dosing a larger proportion (30%) of plasma ACR was converted to the epoxide metabolite glycidamide (GLY) than was observed following subacute i.p. intoxication (8%). This subchronic effect was not specifically related to changes in enzyme activities involved in GLY formation (cytochrome P450 2E1) or metabolism (epoxide hydrolases). Both ACR and GLY formed hemoglobin adducts during subacute and subchronic dosing, the absolute quantity of which did not change as a function of neurotoxicant exposure. Compared to subacute i.p. exposure, the subchronic schedule produced approximately 30% less ACR adducts but two-fold more GLY adducts. GLY has been considered to be an active ACR metabolite and might mediate axon degeneration during subchronic ACR administration. However, corresponding peak GLY plasma concentrations were relatively low and previous studies have shown that GLY is only a weak neurotoxicant. Our study did not reveal other toxicokinetic idiosyncrasies that might be a basis for subchronic induction of irreversible axon damage. Consequently the mechanism of axon degeneration does not appear to involve route- or rate-dependent differences in metabolism or disposition.

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