2-tert-butylhydroquinone

Toxicity to reproduction

Administrative data

Endpoint:

one-generation reproductive toxicity

Remarks:

based on test type (migrated information)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Justification for type of information:

Data is from a NTP report.

Data source

Reference

Reference Type:

other: Authoritative data base

Title:

Toxicology and Carcinogenesis Studies of t-Butylhydroquinone (CAS No. 1948-33-0) in F344/N Rats and B6C3F(1) Mice (Feed Studies)

Author:

National Toxicological Program

Year:

1997

Bibliographic source:

NTP (National Toxicological Program)by Agency for Toxic Substances and Disease Registry:- NTP Technical Report Series No. 459, 1997 May; 1-326

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other:

Principles of method if other than guideline:

The 13-week study was performed to evaluate the cumulative toxic effects of test chemical with exposure to the chemical in Male and female F344/N rats and also to determine the dose levels to be used in the long-term study.

GLP compliance:

no

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2-tert-butylhydroquinone

EC Number:

217-752-2

EC Name:

2-tert-butylhydroquinone

Cas Number:

1948-33-0

Molecular formula:

C10-H14-O2

IUPAC Name:

2-tert-butylbenzene-1,4-diol

Test material form:

solid: particulate/powder

Remarks:

migrated information: powder

Details on test material:

- Name of test material (as cited in study report):2-tert-butylhydroquinone
- Molecular formula (if other than submission substance): C10H14O2
- Molecular weight (if other than submission substance): 166.22
- Substance type:Organic
- Physical state: solid
- Impurities (identity and concentrations):99%

Specific details on test material used for the study:

- Molecular weight (if other than submission substance): 166.22 g/mol
- Substance type:Organic
- Physical state: solid
- Impurities (identity and concentrations):99%

Test animals

Species:

rat

Strain:

other: F344/N

Details on species / strain selection:

No Data Available

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
Males acquired for the reproductive toxicity phase were used for breeding purposes only and were not considered part of the study.
- Source: Taconic Farms (Germantown, NY).
- Age at study initiation: F: 57 day old
- Housing: Polycarbonate cages with bedding
- Diet (e.g. ad libitum): NIH-07 open formula mash diet, ad libitum
- Water (e.g. ad libitum): Tap water via automatic watering system; available ad libitum
- Acclimation period: 19 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18.7°C to 24.2°C
- Humidity (%): 35.8 %-79.3 %
- Air changes (per hr): minimum of 10 changes per hour
- Photoperiod (hrs dark / hrs light): 12 hours/day

Administration / exposure

Route of administration:

oral: feed

Vehicle:

other: NIH-07 open formula mash diet

Details on exposure:

Fo - Approximately 10 weeks
F1 - 87-89 days (clinical pathology study F1 rats)
93-94 days (core study F1 rats)

Details on mating procedure:

- M/F ratio per cage: 1:2
- Proof of pregnancy: Vaginal smears were taken daily from breeder females to determine the presence of sperm.
- After successful mating each pregnant female was caged (how): Females were housed individually when pregnancy was confirmed

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The dose formulations for the 13-week study were prepared weekly. Homogeneity and stability analyses of the dose formulations were conducted by the analytical chemistry laboratory using high-performance liquid chromatography. Homogeneity was confirmed, and the stability of the dose formulations was confirmed for at least 3 weeks when stored in sealed containers in the dark at 5 ° C. For the 13-week studies, dose formulations were analyzed at the beginning, in the middle, and at the end of the studies. Of the dose formulations used in the 13-week studies, 98% were within 10% of the target concentration with no value greater than 16% from the target concentration.

Duration of treatment / exposure:

F0 generation exposed approximately for 10 weeks

F1 generation exposed to test chemical for 87-89 days (clinical pathology study F1 rats)
and 93-94 days (core study F1 rats)

Frequency of treatment:

Daily

Details on study schedule:

Fo generation - 10 females
F1 generation
Core study - I0 males and 10 females
Clinical pathology study - 10 males and 10 females were used.
Since Males acquired for the reproductive toxicity phase were used for breeding purposes only males not considered as part of the study

Doses / concentrations

Remarks:

Doses / Concentrations: 0, 250, 500, 1000, 2000 or 4000 mg/kg bw

Basis:
nominal in diet Approx 0, 2500, 5000, 10000, 20000, or 40000 ppm

No. of animals per sex per dose:

Control: 10 females
2500 ppm (250 mg/kg): 10 females
5000 ppm (500 mg/kg): 10 females
10000 ppm (1000 mg/kg): 10 females
20000 ppm (2000 mg/kg): 10 females
40000 ppm (4000 mg/kg): 10 females

Control animals:

yes, concurrent vehicle

Details on study design:

Groups of 10 female rats (F0 generation) were fed diets containing Approx 0, 250, 500, 1000, 2000 or 4000 mg/kg of test chemial for approximately 10weeks. During cohabitation two F0 females were housed with one breeder male.Clinical findings and body weights were also recorded weekly during lactation. Rats that did not litter by day 25 were killed and uteri were stained with ammonium sulfide and examined for implantation sites. After parturition, on day 4 postpartum, litters were randomly culled to a maximum of eight rat pups per litter; pup weights were recorded on days 4, 11, 18, and 28. Pups were weaned on day 28.

Male and female F344/N rats for the 13-week base study were offspring (F1 generation) of the breeders from the perinatal phase of the study. Rats were approximately 34 days old: on the first day of the study.. Groups of 10 male and 10 female F1 rats were fed diets containing 0, 250, 500 and 1000mg/kg of test chemical for 13 weeks after weaning. (No F1 offspring resulted from F 0 females fed diets containing 2000 and 4000mg/kg doses so these exposure levels were not used in the 13-week rat study). Clinical findings were recorded and the animals were weighed initially, weekly, and at the end of the study; feed consumption was recorded as an average of grams per animal per day.

Blood samples was collected at week 13 from core study (F1) for clinical pathology analyses .At the end of the study, samples from 0, 250, 500 and 1000mg/kg group F1 rats were collected for sperm motility and vaginal cytology evaluations. A necropsy was performed on all core study F1 animals.

Positive control:

No Data Available

Examinations

Parental animals: Observations and examinations:

F0 females were observed twice daily.
Clinical findings, body weights, and feed consumption were recorded weekly during the first 2 weeks of the study (prior to cohabilation; clinical findings and body weights were also recorded weekly during lactation.


F1 generation were observed twice daily.
Clinical findings were recorded and the animals were weighed initially, weekly, and at the end of the study; feed consumption was recorded as an average of grams per animal per day.

Blood samples was at 13 week from core study (F1), sperm motility and vaginal cytology evaluations and necropsy was performed on all core study F1 animals.

Oestrous cyclicity (parental animals):

From F1 generation, for 7 consecutive days prior to scheduled terminal sacrifice, the vaginal vaults of the females were moistened with saline and samples were collected Relative numbers of leukocytes, nucleated epithelial cells and large squamous epithelial cells were determined and used to ascertain estrous cycle stage. (i.e.,diestrus, proestrus, estrus, and metestrus).

Sperm parameters (parental animals):

Male rats from F1 generation were evaluated for sperm count and motility.

Litter observations:

After parturition in F0 generation, pups were examined and the number and sex of pups and the litter weight were recorded. Pup weights were recorded on days 4, 11, 18, and 28.

Postmortem examinations (parental animals):

F0 generation rats that did not litter by day 25 were killed and uteri were stained with ammonium sulfide and examined for implantation sites.

Postmortem examinations (offspring):

A necropsy was performed on all core study F1 animals. The heart, right kidney, liver, lungs, right testes, and thymus were weighed. Tissues for microscopic examination were fixed and preserved in 10% neutral buffered formalin, processed and trimmed, embedded in paraffin, sectioned to a thickness of 5 to 6 um, and stained with hematoxylin and eosin. A complete histopathologic examination was performed on all control and 1000mg/kg rats. Additionally, the following tissues from selected exposure groups were examined: the nose of all exposed groups of male rats and 500mg/kg female rats; the spleen of 500 and 1000 mg/kg group male rats and all exposed groups of female rats; the mesenteric lymph node of 500mg/kg female rats; and the kidneys of 250 and 1000mg/kg female rats.

Reproductive indices:

No data

Offspring viability indices:

No data

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Hair discoloration of all the treated groups were observed.

Body weight and weight changes:

not examined

Food consumption and compound intake (if feeding study):

not examined

Organ weight findings including organ / body weight ratios:

not examined

Histopathological findings: non-neoplastic:

not examined

Other effects:

not examined

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

effects observed, treatment-related

Description (incidence and severity):

Dams exposed to 2000 or 4000 mg/kg did not litter.

Details on results (P0)

No effect on gestation length, the average number of pups born per litter, or the number of dams with stillborn pups for dams up to 1000 mg/kg

Effect levels (P0)

Dose descriptor:

NOAEL

Effect level:

ca. 250 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

female

Basis for effect level:

other: No effect on gestation length, the average number of pups born per litter, the number of dams with stillborn pups, number of pup deaths or mean body weight of pups

Results: F1 generation

General toxicity (F1)

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Hair discoloration was observed in all exposed groups of rats, with the exception of 250mg/kg females.

Mortality / viability:

mortality observed, treatment-related

Description (incidence and severity):

More number of pup deaths in 500 and 1000 mg/kg group than that of the control animals.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Mean body weight reduced in 500 and 1000 mg/kg group compared to control animals.

Haematological findings:

no effects observed

Description (incidence and severity):

Serum bile acid levels were generally significantly increased in 500 and 1000mg./kg male and female rats at day 5, at week 3, and at the end of the study.

Serum alanine aminotransferase activity levels were increased at day 5 in females exposed to 1000mg/kg, at week 3 in males and females exposed to 250, 500, or 1000mg/kg, and at the end of the study in males receiving 250mg/kg. However, because the increases observed in these two parameters were marginal hence not considered as biologicaly significant change.

Sexual maturation:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

Differences in absolute and/or relative organ weights of control and exposed groups occured but these changes were not considered to be terst chemical related.

Gross pathological findings:

not examined

Histopathological findings:

effects observed, treatment-related

Description (incidence and severity):

Increased incidences of hyperplasia of the nasal respiratory epithelium were observed in males exposed to 500mg/kg and males and females exposed to 1000mg/kg, andan increased incidence of nasal exudate was observed in males in the 1000mg/kg group.

Increased incidences of splenic pigmentation were observed in males and females exposed to 500 and 1000mg/kg and incidences of atrophy of the red
pulp were observed in these groups of females.

Other effects:

effects observed, treatment-related

Description (incidence and severity):

The mean spermatid count, spermatid heads per testis and spermatid heads per gram of testis were significantly decreased in F1 males exposed to 500mg/kg and estrous cycles of F1 females exposed to 250 and 500mg/kg were significantly longer than that of the
controls.

Effect levels (F1)

Key result

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

250 mg/kg diet

Based on:

test mat.

Sex:

male/female

Basis for effect level:

clinical biochemistry

organ weights and organ / body weight ratios

histopathology: non-neoplastic

Overall reproductive toxicity

Reproductive effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

The NOAEL for test chemical in parental female F344/N rats was determined to be approximately 250 mg/kg bw.

Executive summary:

The study was performed to evaluate the cumulative toxic effects of test chemical on the F344/N rats. The test chemical was fed to female F344/N rats (F0 generation) at a doses of  0, 2500, 5000, 10000, 20000, or 40000 ppm (Approx 250, 500, 1000, 2000 or 4000 mg/kg bw) in diet for approximately 10 weeks (from 2 weeks prior to cohabitation until weaning of F1 pups). Clinical findings, body weights, and feed consumption were recorded weekly for F0 females during the first 2 weeks and during lactation. No effect was observed on gestation length, the average number of pups born per litter, or the number of dams with stillborn pups for dams up to 1000 mg/kg. The dams exposed to 2000 or 4000 mg/kg did not litter. In the 500 and 1000 mg/kg group, more number of pup deaths and reduction in mean body weights of pups at weaning was observed. The average number of surviving pups per litter in the 1000 mg/kg group was lower as compared to the controls. Male and female F344/N rats for the 13-week base study were offspring (F1 generation) of the breeders from the perinatal phase of the study. Rats were approximately 34 days old: on the first day of the study.. Groups of 10 male and 10 female F1 rats were fed diets containing 0, 250, 500 and 1000 mg/kg of test chemical for 13 weeks after weaning. (No F1 offspring resulted from F0 females fed diets containing 2000 and 4000mg/kg doses so these exposure levels were not used in the 13-week rat study). Clinical findings were recorded and the animals were weighed initially, weekly, and at the end of the study; feed consumption was recorded as an average of grams per animal per day. Blood samples was collected at week 13 from core study (F1) for clinical pathology analyses .At the end of the study, samples from 0, 250, 500 and 1000mg/kg group F1 rats were collected for sperm motility and vaginal cytology evaluations. A necropsy was performed on all core study F1 animals. The results (F0 generation) of the study revealed no effect on gestation length, the average number of pups born per litter, the number of dams with stillborn pups(F0 generation) and dams exposed to 2000 or 4000 mg/kg did not litter. The results of the F1 generation rats revealed, hair discoloration in all except 250mg/kg treated rats. More number of pup deaths in 500 and 1000 mg/kg group than that of the control animals. Serum bile acid levels (in 500 and 1000mg./kg male and females and Serum alanine aminotransferase activity levels (in 250, 500 and 1000 mg/kg group males and female) were increased as comapred to control but not considered to be biologically significant. Increased incidence of hyperplasia of nasal respiratory epithelium (500 and 1000mg/kg) and increased incidences of splenic pigmentation (500 mg/kg and 1000 mg/kg) Thus, based on all the conclusions, the NOAEL for test chemical in F344/N rats was determined to be approximately 250 mg/kg bw.