Phenol, heptyl derivs.

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: Peer reviewed literature

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

publication

Title:

Quinone methode formation from para isomers of methylphenol (cresol), ethylphenol and isopropylphenol: Relationship to toxicity

Author:

Thompson DC, Perera K and London R

Year:

1995

Bibliographic source:

Chem. Res. Toxicol. 8: 55-60

Materials and methods

Objective of study:

metabolism

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Test compounds (2 mM each) were dissolved in DMSO and added to pre-incubated rat liver slices (30 min at 37°C in 20 mL glass scintillation vials containing 2.5 mL Krebs-Hepes buffer (pH 7.4)) at a volume of 25 µL (1% v/v) and incubated for up to 6 h. Toxicity was measured as loss of intracellular potassium using a flame photometer ( liver slices removed at appropriate time intervals dried, washed and acidified before centrigugation for 10 minutes and dilution with water).
Microsoms for metabolite formation were prepared from similar rat livers to those used from the slice assays. Incubation at 37°C was performed for various time periods and stopped by acidification. Metabolism was analysed using HPLC, MS and Proton NMR.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

4- methylphenol, 4-ethylphenol, 4-isopropylphenol

IUPAC Name:

4- methylphenol, 4-ethylphenol, 4-isopropylphenol

Details on test material:

The test substances are structural analogs of the reference substance. Readacross of data is therefore applicable.
Purity: not specified but indicated to be of highest quality available.
[3H] Glutathione: 44 Ci/mmol

Radiolabelling:

yes

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Laboratories, Indianapolis, IN, USA
- Weight at study initiation: 200 - 225 g

Administration / exposure

Route of administration:

other: rats were not dosed, only liver and liver extracts used

Vehicle:

DMSO

Details on exposure:

Rat liver slices or rat liver micrsommes incubated with test material for up to 6 hours

Duration and frequency of treatment / exposure:

Up to 6 hours

Doses / concentrations

Remarks:

Doses / Concentrations:
rat liver slices: 1% v/v
Microsomes: 1 mM

No. of animals per sex per dose / concentration:

Not stated.

Control animals:

yes, concurrent vehicle

Positive control reference chemical:

Not applicable

Details on study design:

Test compounds (2 mM each) were dissolved in DMSO and added to pre-incubated rat liver slices (30 min at 37°C in 20 mL glass scintillation vials containing 2.5 mL Krebs-Hepes buffer (pH 7.4)) at a volume of 25 µL (1% v/v) and incubated for up to 6 h. Toxicity was measured as loss of intracellular potassium using a flame photometer ( liver slices removed at appropriate time intervals dried, washed and acidified before centrigugation for 10 minutes and dilution with water).
Microsoms for metabolite formation were prepared from similar rat livers to those used from the slice assays. Incubation at 37°C was performed for various time periods and stopped by acidification. Metabolism was analysed using HPLC, MS and Proton NMR.

Details on dosing and sampling:

No data

Statistics:

No data

Results and discussion

Preliminary studies:

No data

Toxicokinetic / pharmacokinetic studies

Details on absorption:

No data

Details on distribution in tissues:

No data

Details on excretion:

No data

Metabolite characterisation studies

Metabolites identified:

yes

Details on metabolites:

A single glutathione conjugate peak detected for each compound. Peaks were not observed in absence of glutathione. The rate of formation of the glutathione peak mirrors the toxicity of the parent material. Splitting of the conjugate peak shows two distinct forms suggesting diastereomeric conjugates. MS confirmed that the conjugates are monoglutathione conjugates where the glutathione is attached to the benzylic carbon. This is consistent with the formation of reactive quinone methide intermediates

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): other: possible metabolic pathway in liver identified
Rat liver microsomes initiated the metabolisation of simple alkyl phenols to quinone methides.

Executive summary:

Test Guidance

No Guideline followed

Method and material

Test compounds (2 mM each) were dissolved in DMSO and added to pre-incubated rat liver slices (30 min at 37°C in 20 mL glass scintillation vials containing 2.5 mL Krebs-Hepes buffer (pH 7.4)) at a volume of 25 µL (1% v/v) and incubated for up to 6 h. Toxicity was measured as loss of intracellular potassium using a flame photometer ( liver slices removed at appropriate time intervals dried, washed and acidified before centrigugation for 10 minutes and dilution with water). Microsoms for metabolite formation were prepared from similar rat livers to those used from the slice assays. Incubation at 37°C was performed for various time periods and stopped by acidification. Metabolism was analysed using HPLC, MS and Proton NMR.

Results

A single glutathione conjugate peak was detected for each compound. Peaks were not observed in absence of glutathione. The rate of formation of the glutathione peak mirrors the toxicity of the parent material. Splitting of the conjugate peak shows two distinct forms suggesting diastereomeric conjugates. MS confirmed that the conjugates are monoglutathione conjugates where the glutathione is attached to the benzylic carbon. This is consistent with the formation of reactive quinone methide intermediates

Conclusions

Rat liver microsomes initiated the metabolisation of simple alkyl phenols to quinone methides.