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Toxicological information

Basic toxicokinetics

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Administrative data

Endpoint:
basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
no data
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: An other test substance was used, 2,3,6-trimethylphenol was identified as metabolite.

Data source

Reference
Reference Type:
publication
Title:
Distribution and metabolism of 1,2,4-trimethylbenzene (pseudocumene) in the rat.
Author:
Huo Ji-Z et al.
Year:
1989
Bibliographic source:
Xenobiotica 19: 161-170.

Materials and methods

Objective of study:
distribution
metabolism
Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Rats were fasted overnight before receiving an oral dose 1,2,4-trimethylbenzene. The animals were transferred to separate metabolism cages and urine was collected over ice for 24 h. Water was freely available during the collection period. Urine or urine hydrolysates were analysed for free and total (conjugated) metabolites using gas-liquid chromatography-mass spectrometry (GLC-MS)
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): 14C-1,2,4-trimethylbenzene (CAS No. 95-63-6),
Radiolabelling:
yes
Remarks:
14C

Test animals

Species:
rat
Strain:
Wistar
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Weight at study initiation: approximately 200 g
- Fasting period before study: overnight
- Individual metabolism cages: yes

ENVIRONMENTAL CONDITIONS
- No data

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
olive oil
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
0.8mmol ≡ 0.49 µCi/kg in olive oil (48 mg/ml)
Duration and frequency of treatment / exposure:
once
Doses / concentrations
Remarks:
Doses / Concentrations:
Distribution: 0.8mmol ≡ 0.49 µCi/kg in olive oil (48 mg/ml).
Metabolism: 0.08 mmol/kg or 0.8 mmol/kg in olive oil (4.8 or 48 mg/ml).
No. of animals per sex per dose:
3
Control animals:
no
Positive control:
no
Details on study design:
Tissue distribution study:
- Rats received an oral dose of 14C-124TMB, were transferred to separate metabolism cages and killed at different times.
- Samples of blood, major organs, muscle and adipose tissue were removed and weighed. Any urine voided prior to slaughter was also collected. The total weights of muscle, adipose tissue, skin and serum were calculated according to the method of Adolph (1949).
- Approximately 100 mg of each tissue was placed separately in glass screw-cap vials and Soluene® (Packard Instrument Co., 0.5 ml) was added. After sealing, the vials were incubated at 70°C overnight. Highly coloured samples (e.g. spleen, lung) were bleached by the addition of H202 (30% w/v, 0.1 ml) and allowing to stand for at least 1 hour.
- After addition of Insta-Gel® (Packard Instrument Co., 5 ml) the radioactivity was determined in an LKB Rackbeta II liquid scintillation counter operated in the external standard channels ratio mode. Counting efficiency was determined by reference to a previously prepared quench curve.

Metabolism study:
Rats received 124TMB, were transferred to separate metabolism cages and urine was collected over ice for 24 h. Water was freely available during the collection period. Urine samples were stored frozen until required for analysis.
Urine extracts were prepared for analysis of free and total (conjugated) metabolites. Recoveries from urine of rats dosed with 14C-124TMB showed that this method recovered 87.7% (range 86-90%, n=3) of the radioactivity. Urine or urine hydrolysates were analysed by GLC-MS using a Hewlett Packard 5890 GC coupled with an HP 5970 mass selective detector and an HP 59970A data system.
Details on dosing and sampling:
PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled (delete / add / specify): blood, major organs, muscle, adipose tissue and urine
- Time and frequency of sampling: 3, 6, 12 and 24 hours after treatment

METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled (delete / add / specify): urine, faeces, tissues, cage washes, bile
- Time and frequency of sampling:
- From how many animals: (samples pooled or not)
- Method type(s) for identification (e.g. GC-FID, GC-MS, HPLC-DAD, HPLC-MS-MS, HPLC-UV, Liquid scintillation counting, NMR, TLC)
- Limits of detection and quantification:
- Other:


TREATMENT FOR CLEAVAGE OF CONJUGATES (if applicable):
Statistics:
no data

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on absorption:
No data
Details on distribution in tissues:
14C-124TMB was rapidly and widely distributed throughout the body with the highest levels in adipose tissue. No other preferential uptake of 14C-124TMB by any of the organs or tissues examined was evident. Tissue levels declined rapidly within 24h after dosage, with more than 99% of the administered radioactivity recovered in the urine during this period.
Details on excretion:
No data

Metabolite characterisation studies

Metabolites identified:
yes
Details on metabolites:
2,3,6-trimethylphenol was identified as a metabolite of 124TMB.
A complex mixture of isomeric trimethylphenols, dimethylbenzyl alcohols, dimethylbenzoic acids and dimethylhippuric acids excreted in the urine accounted for more than 81% of the administered dose. The major metabolites were 3,4-dimethylhippuric acid (30.2 %dose), 2,4 -dimethylbenzyl alcohol (12.7% dose, primarily as sulphate and glucuronide conjugates) and 2,5-dimethylbenzyl alcohol (11.7% dose, primarily as sulphate and glucuronide conjugates). The influence of steric factors on oxidation at aromatic carbon adjacent to methyl substituent site appears to be minimal given that the proportion of the phenolic metabolites, including 2,3,6-trimethylphenol with 4.0 % are formed in approximately equal proportions.
 

Applicant's summary and conclusion