Registration Dossier

Administrative data

Endpoint:
basic toxicokinetics
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1968

Materials and methods

Objective of study:
absorption
excretion
metabolism
Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 417 (Toxicokinetics)
Version / remarks:
-reliability scoring based on 1984 guideline
Deviations:
yes
Remarks:
-full details of the study design was not provided
GLP compliance:
no
Remarks:
Study pre-dates GLP

Test material

Reference
Name:
Unnamed
Type:
Constituent

Test animals

Species:
rat
Strain:
other: Carworth Farm Elias
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Not reported
- Age at study initiation: approximately 5 weeks
- Weight at study initiation: Not reported
- Fasting period before study: Not reported
- Housing: Housed individually in metabolism cages
- Individual metabolism cages: yes
- Diet (e.g. ad libitum): Not reported
- Water (e.g. ad libitum): Not reported
- Acclimation period: 3 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): Not reported
- Humidity (%): Not reported
- Air changes (per hr): Not reported
- Photoperiod (hrs dark / hrs light): Not reported

Administration / exposure

Route of administration:
oral: feed
Vehicle:
other: Feed
Duration and frequency of treatment / exposure:
Daily for a period of 35 days
Doses / concentrationsopen allclose all
Dose / conc.:
12 500 ppm
Remarks:
corresponding to 230 - 287 mg/kg body weight
Dose / conc.:
50 000 ppm
Remarks:
corresponding to 850 - 1112 mg/kg body weight
No. of animals per sex per dose:
6 males/group
Control animals:
yes, plain diet
Positive control:
None used.
Details on study design:
Groups of rats were given either a control diet or a diet containing 1.25 or 5.0% of the test item daily for 35 days.

Separate portions of each urine sample were analysed for the test item in the free form and as the glucuronide conjugate. In urine samples, glucuronic acid was determined before and after hydrolysis with beta-glucuronidase. Urinary test material was calculated from the increased amount of glucuronic acid found after hydrolysis, assuming an equimolar relationship between the two. Faecal levels of the test item were based on the increased weight of evaporated acetone extracts of faeces, since the test item is highly soluble in acetone. Paper chromatography and spectrophotometric analysis were used to establish that conjugated test material was excreted in the urine, and that the test item appeared unchanged in the faeces.
Details on dosing and sampling:
PHARMACOKINETIC STUDY (Absorption, metabolism, and excretion)
- Tissues and body fluids sampled: urine, faeces, kidney and liver tissues
- Time and frequency of sampling: Daily samples of urine and faeces were collected from each animal. Two animals from each group were sacrificed on Days 11, 22, and 35, and liver and kidney tissues were taken for microscopic examinations.

METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled: urine, faeces, kidney and liver tissues
- Time and frequency of sampling: Daily samples of urine and faeces were collected from each animal. After 11, 22, and 35 days, 2 animals from each group were sacrificed, and liver and kidney tissues were taken for microscopic examinations.
- From how many animals: Samples were not pooled (individual data were provided from each animal); however, several samples were pooled when examining ethereal sulphate conjugation.
- Method type(s) for identification: paper chromatography, spectrophotometric analysis
- Limits of detection and quantification: not reported

Results and discussion

Preliminary studies:
Preliminary short-term feeding studies with the test item in male rats indicated that most of the material was excreted in the faeces, while the remainder of the compound was absorbed, conjugated, and excreted as a glucuronide in the urine. In order to study the absorption and excretion of the test item in male rats over a longer period, a study was initiated with dietary concentrations of 1.25 and 5.0% test material.

Toxicokinetic / pharmacokinetic studies

Details on absorption:
The authors reported that the test item has low absorption after oral intake.
Details on excretion:
The daily recovery of unchanged test material from the faeces was about 90%.

Metabolite characterisation studies

Metabolites identified:
yes
Details on metabolites:
The conjugation and urinary excretion of the test item glucuronide in animals on both dietary levels was about 10% of the dose over the 35-day test period.

Any other information on results incl. tables

The Rf values determined by paper chromatography of the pure compounds were 0.15 for glucuronic acid, 0.57 for test material glucuronide, 0.94 for the test item, and 0.98 for 2-hydroxy-4-n-octoxybenzhydrol. The acetone-soluble material from faeces and the aglycone from enzymic hydrolysis of the urinary glucuronide had the same Rf value as the test item.

In addition to paper chromatography, spectrophotometric analysis was used to confirm the fact that the residues of the faecal extracts contained the test article only and not its metabolite. A portion of the acetone-extracted residue of the faeces of rats fed 5.0% of the test item was analysed for its test material content. The compound comprised 90.1% of the residue. Thus, about 10% of the extracted material represented other acetone-soluble material. Over the 35-day test period, the weights of the residues of acetone extracts of the faeces of control rats and of those fed the test item were determined daily. The weights of the control residues,when expressed as percentages of the weights of the residues from the rats fed 5.0% test article, had a grand mean of 5.8%. The daily mean values ranged from 3.9 to 6.9%. These figures compare favourably with the 10% figure obtained by actual analysis of a faecal sample for the test item.

 

Several of the pooled, daily urine samples from rats fed the test item were examined for an increase in ethereal sulphate conjugation but no evidence for such an increase was found. No significant gross lesions were observed in the rats killed after 11, 22, or 35 days on test. Histological observation did not reveal any lesions in the liver or kidneys of these animals.

The authors also noted that the possibility of an enterohepatic circulation in the metabolic process has not been excluded.

Since, in the present work, hydrolysis of urine samples with beta-glucuronidase gave a product with an Rf value identical with that of unmodified test material, it appears that the test item, too, is conjugated directly without prior reduction of the keto group.

Applicant's summary and conclusion

Conclusions:
no bioaccumulation potential based on study results