Di-tert-butyl α,α,α',α'-tetramethyl-(p-phenylenedimethylene) diperoxide

Repeated dose toxicity: oral

Administrative data

Endpoint:

short-term repeated dose toxicity: oral

Remarks:

combined repeated dose and reproduction / developmental screening

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

26 feb 2007 to 30 april 2007

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: 1a: Guideline study, GLP

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2008

Report date:

2008

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

[1,3(or 1,4)-phenylenebis(1-methylethylidene)]bis[tert-butyl] peroxide

EC Number:

246-678-3

EC Name:

[1,3(or 1,4)-phenylenebis(1-methylethylidene)]bis[tert-butyl] peroxide

Cas Number:

25155-25-3

IUPAC Name:

1,4-bis[1-(tert-butylperoxy)-1-methylethyl]benzene

Constituent 2

Reference substance name:

1,3(4)-bis(tert-butylperoxyisopropyl)benzene

IUPAC Name:

1,3(4)-bis(tert-butylperoxyisopropyl)benzene

Test material form:

solid: particulate/powder

Remarks:

migrated information: powder

Details on test material:

- Name of test material (as cited in study report): 2,2-Bis(t-butylperoxyisopropyl)benzene (CAS 25155-25-3)
- Physical state: pale yellow solid, acrid odour
- Analytical purity: 96.5 %
- Stability under test conditions: at least 4 hours in the vehicle
- Storage condition of test material: room temperature (15-25 °C), dark
- Frequence of dose formulation: weekly, based on a previous results

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: RCC Ltd
- Age at study initiation: 8 weeks (males) and 10 weeks (female)
- Weight at study initiation: 243-291 g (males) and 190-217 g (females)
- Fasting period before study:overnight
- Housing:in Marolon cages ( individually during the pre-pairing period et after the mating , and one male/one female during the paring period)
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 7 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19-25
- Humidity (%): 30-70
- Air changes (per hr): 10-15
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
in corn oil, the dosing solutionsn were made weekly

VEHICLE
- Justification for use and choice of vehicle: justified by analytical considerations
- Concentration in vehicle: 0, 25, 75 or 250 mg/ml
- Amount of vehicle (if gavage): 4 mL/kg
- Lot/batch no. : 38679499

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples of the dose formulations were taken during the first and the last week of the administration period. Three samples were taken from the top, middle and bottom of each formulation, dilution were performed then the samples were analysed with HPLC. Furthemore samples were taken for analysing the stability after 2 and 16 days. The application formulations investigated during the study were found to comprise 2,2-Bis(t-butylperoxy isopropyl)benzene in the range from 81.8% to 118.3% and, thus, the required content limit of ±20% with reference to the nominal concentration was met.

Duration of treatment / exposure:

The test item was administered for at least 44 days.
Females: The test item was administered throughout the pre-pairing (14 days), pairing , gestation (21 days) and lactation periods (until day 4 of post-partum)
Males: dosing of males was continued until the first dams had reached day 4 post partum

Frequency of treatment:

once daily

Doses / concentrations

Remarks:

Doses / Concentrations:
100, 300 and 1000 mg/kg bw/d
Basis:
actual ingested

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Dose levels were selected in agreement with the Sponsor, based on the results of a preliminary dose range-finding study (RCC Study No. A77242)
- Prior to start of treatment, parental animals were assigned to the different groups using a computer-generated random algorithm. In addition, body weights (recorded on the day of allocation) were taken into consideration in order to ensure similar mean body weights in all groups.

Positive control:

no

Examinations

Observations and examinations performed and frequency:

MORTALITY:
- All animals were checked at least twice daily for mortality

SIGNS AND/OR SYMPOTMS:
- All animals were observed at least twice daily for signs of reaction to treatment and/or symptoms of ill health. Additionally, the females were observed for signs of difficult or prolonged parturition.

FUNCTIONNAL OBSERVATION BATTERY (FOB):
- Time schedule: at one time during the stuy (males: shortly before sacrifice; females: on day 3 or 4 post-partum)
- Cage side observations were included: unusual body movements (tremor, convulsions), abnormal behavior (circling, stereotypy), posture, resistance to removal
- Hand-held observations: palpebral closure, pinna, reflex, lacrimation, pupil size, pupil reactivity, salivation, muscle tone, extensor thrust response, righting reflex, and reactivity to handling.
- Open field observations: level of ambulatory activity including rearing (one minute evaluation), responsiveness to sharp noise, paw pinch, gait evaluation, quantity of urine and fecal pellets voided.
- Categorical observations (can be made any time during the FOB): hair coat, behaviour, respiration, muscle movements, eyes, hearing ability (Preyer’s reflex), urine or feces, soiling, general abnormalities, posture
- Measurements / Counts: hind limb / fore limb grip strength, landing foot splay, rectal temperature.

DETAILED CLINICAL OBSERVATIONS:
- Following observations were included: changes in skin, fur eyes, mucous membranes, occurence of secretions and excretions and autonomic activity (lacrimation, piloerection, pupil size, unusual respiratory pattern)
-Time schedule: once prior to the first item administration and weekly thereafter

BODY WEIGHT
- The animals were weighed daily during the entire study.

FOOD CONSUMPTION AND COMPOUND INTAKE:
- Males: Food consumption was recorded weekly during the prepairing and post-pairing period.
Females: Food consumption was recorded for the following periods: days 1-8 and 8-14 of the pre-pairing period; days 0-7, 7-14 and 14-21 post coitum and days 1-4 post partum.
- Food consumption was not recorded durin the pairing period

OPHTHALMOSCOPIC EXAMINATION: Not analysed

HAEMATOLOGY AND CLINICAL CHEMISTRY:
- Time schedule for collection of blood: early in the morningn on the day before or on the day of scheduled necropsy for malesn abd on day 5 of postpartum for female
- Anaesthetic used for blood collection: Yes
- Animals fasted: Yes
- How many animals: from all P generation males and females
- Following parameters were examined for hameatology
1/Complete blood cell count: Erythrocyte count, Hemoglobin, Hematocrit, Mean corpuscular volume, Red cell volume distribution width
Mean corpuscular hemoglobin, Mean corpuscular hemoglobin concentration, Hemoglobin concentration distribution width, Reticulocyte count, Reticulocyte maturity index, Leukocyte count total, Differential leukocyte count (Neutrophils, Eosinophils, Basophils, Lymphocytes, Monocytes, Large unstained cells) Platelet count
2/ Coagulation: Prothrombin time (=Thromboplastin time), Activated partial thromboplastin time
- Following parameters were examined for clinical chemistry : Glucose, Urea, Creatinine, total Bilirubin, Bile acids, total Cholesterol, ALAT, ASAT, PAL, Gamma-GT, Sodium, Potassium, Chloride, Calcium, Phosphorous, total Protein, albumine, Globulin

URINALYSIS: only discolorations were reported

OTHER: The females were observed twice daily for signs of difficult or prolonged parturition

Sacrifice and pathology:

GROSS PATHOLOGY: The animals were examined macroscopically for any structural abnormalities or pathological changes, with special attention paid to the organs of the reproductive system

ORGAN WEIGHT
The testes and epididymes of all parental males were weighed.
In addition for five adult males (all groups) and for five females (groups 1 and 2), six females (group 3) and all females (group 4), randomly selected from each group, the following organs were trimmed from any adherent tissue, as appropriate, and their wet weight taken: live, spleen, adrenals, brain, thymus, heart, kidneys:

HISTOPATHOLOGY: Full histopathology was carried out on the preserved organs and tissues of the animals in the vehicle control and high dose group (with special emphasis on stages of spermatogenesis and histopathology of interstitial testicular cell structure). Examinations were extended to the animals of the other dosage groups, if treatment-related changes were seen in the highest dose group.

Tissur preservation
- For all animals: prostate, testes, seminal vesicles with coagulation gland, epididymides, ovaries
- In addition, of the five males (all groups) and of five females (groups 1 and 2), six females (group 3) and all females (group 4), selected for organ weights, the following tissues were preserved: gross lesions, heart, brain, thymus, spinal cord, thyroid, small and large intestines, trachea and lungs, stomach, uterus (with vagina), liver, urinary bladder, kidneys, lymph nodes (mandibular, mesentericl), adrenals, peripheral nerve, spleen, bone marrow

Histological examination of ovaries was carried out on any female that did not give birth. Microscopic examination of the reproductive organs of all infertile males was made, if necessary.

All gros lesions were examined.

Other examinations:

In addition for five adult males (all groups) and for five females (groups 1 and 2), six females (group 3) and all females (group 4), randomly selected from each group, the following organs were trimmed from any adherent tissue, as appropriate, and their wet weight taken: live, spleen, adrenals, brain, thymus, heart, kidneys.

Statistics:

For body weights and food consumption
Means and standard deviations of various data were calculated, If the variables could be assumed to follow a normal distribution, the Dunnett
t-test, based on a pooled variance estimate, was used for inter-group comparisons; The Steel test (rank test) was applied when the data could not be assumed tofollow a normal distribution, Fisher's Exact test for 2x2 tables was applied if the variables could be dichotomized without loss of information.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

not examined

Details on results:

BODY WEIGHT:
- decreased only for males in the group 4 (from the day 3 until necropsy), in the group 3 (from day 12 until necropsy) and in the group 2 (from day 5 until necropsy)
- only statistically decreased for females in the groupe 4, during the gestation and lactation periods (not clear in the pre-pairing and pairing periods)

FOOD CONSUMPTION: slight difference (increase or decrease). The food consumption was not the same il all the groups and within all the period (pre-pairing period, pairing period).

ORGAN WEIGHTS (PARENTAL ANIMALS):
- Kidney were statistically significantly increased in group 3 and 4; it may be due to an increased metabolism and excretion of test item, and was therefore considered test item-related

HISTOPATHOLOGY:
- No changes in the reproductive organs
- Centrilobular and/or diffuse hepatocellular hypertrophy in groups 3 and 4, considered as being adaptative changes and not adverse effect of the test item.
- Kidney: slight to moderate diffuse tubulare degeneration/regeneration in all 5 males of group 4, minimal to slight multifocal tubular degeneration/regeneration in 3/5 males of group 3 and 5/10 females of group 4. In addition, slightly increased incidence of focal tubular degeneration/regeneration in females of group 4. Slightly increased incidence and severity of hyaline droplets in proximal convoluted tubules in males of groups 3 and 4.

OTHER FINDINGS: for reproductive data, see the item 7.8.1

Effect levels

1

Dose descriptor:

NOAEL

Effect level:

100 mg/kg bw/day (actual dose received)

Sex:

male

Basis for effect level:

other: Kidney: multifocal tubular degeneration / regeneration

2

Dose descriptor:

dose level:

Effect level:

100 mg/kg bw/day (actual dose received)

Sex:

male/female

Basis for effect level:

other: Increase in kidney/ body weight ratio

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Selected Microscopic Findings for 2,2-Bis(t-butylperoxy isopropyl)benzene in Males:
Groups				1		2		3		4
Dose Levels of 2,2-Bis				0		100		300		1000
(t-butylperoxy isopropyl)benzene				mg/kg/day		mg/kg/day		mg/kg/day		mg/kg/day
Liver(nos. examined)				5		5		5		5
- Centr. hep. hypertrophy Grade 1				0		3		1		0
Grade 2				0		0		3		0
Grade 3				0		0		0		3
Mean Severity				0		1.0		1.8		3.0
- Diff. hep. hypertrophy Grade 1				0		0		1		0
Grade 2				0		0		0		2
Mean Severity				0		0		1,0		2,0
Thyroid gland(nos. examined)				5		0		0		5
- Follic.cell hypertrophy Grade 1				4		0		0		0
Grade 2				0		0		0		4
Grade 3				0		0		0		1
Mean Severity				1.0		0		0		2.2
Kidneys(nos. examined)				5		5		5		5
- Multifocal tubular degener./regeneration Grade 1				0		0		2		0
Grade 2				0		0		1		0
Mean Severity				0		0		1.3		0
- Diffuse tubular degener./regeneration Grade 2				0		0		0		2
Grade 3				0		0		0		3
Mean Severity				0		0		0		2.6
- Hyaline droplets Grade 1				2		2		0		0
Grade 2				0		1		4		3
Grade 3				0		0		1		2
Mean Severity				1.0		1.3		2.2		2.4

Selected Microscopic Findings for 2,2-Bis(t-butylperoxy isopropyl)benzene in Females:
Groups		1		2		3		4
Dose Levels of 2,2-Bis		0		100		300		1000
(t-butylperoxy isopropyl)benzene		mg/kg/day		mg/kg/day		mg/kg/day		mg/kg/day
Liver(nos. examined)		5		5		6		10
- Centr. hep. hypertrophy Grade 1		0		1		2		0
Grade 2		0		0		2		0
Grade 3		0		0		0		5
Mean Severity		0		1.0		1.5		3.0
- Diff. hep. Hypertrophy Grade 1		0		0		2		0
Grade 2		0		0		0		5
Mean Severity		0		0		1.0		2.0
Thyroid gland(nos. examined)		5		0		0		5
- Follic. cell hypertrophy Grade 1		2		0		0		0
Grade 2		0		0		0		1
Grade 3		0		0		0		4
Mean Severity		1,0		0		0		2.8
Kidneys(nos. examined)		5		5		6		10
- Focal tubul. deg./regen. Grade 1		1		2		1		5
Mean Severity		1.0		1.0		1.0		1.0
- Multifocal tubular degener./regeneration Grade 1		0		0		0		3
Grade 2		0		0		0		2
Mean Severity		0		0		0		1.4
- Hyaline casts Grade 1		0		0		0		1
Grade 2		0		0		0		1
Mean severity		0		0		0		1.5
- Pelvic dilation Grade 1		0		0		0		1
Mean Severity		0		0		0		1.0

Applicant's summary and conclusion

Conclusions:

The NOAEL is 100 mg/kg bw/day, based on kidney multifocal tubular degeneration / regeneration in males at 300 mg/kg, and increase in kidney/body weight ratio in males and females at 300 mg/kg. This NOAEL is considered as secure, since effets on kidney are observed at 300mg/kg/day only in males, and at 1000 mg/kg/day both in male in female, and could be at least partially related to a specific specy senstivity (alpha 2 microglobuline?).

Executive summary:

The potential toxic effects of 2,2-Bis(t-butylperoxy isopropyl) benzene following repeated oral exposure, in a combined repeated dose and reproduction/developmental screening study according to the OECD Guideline No. 422.

Four groups of Sprague Dawley rats (10 males and 10 females) were treated orally with 2,2-Bis(t-butylperoxy isopropyl)benzene at 0, 100, 300, 1000 mg/kg/d by gavage. Females were paired with males from the same dose-level group until mating occurred. Gestation was monitored. Females were allowed to deliver normally and to rear their progeny until day 4 post-partum.

Body weights were recorded pre-test, weekly and at death or prior necropsy. Animals were observed daily for toxicity and pharmacological effects, and twice daily for morbidity and mortality. A neurobehavioral examination has been realized before the end of the study. Whole blood, serum and plasma were sampled just prior necropsy and analysed for related haematological and clinical chemistry parameters.

All animals were examined for gross pathology, and organs were weighted and submitted to histopathology.

At any dose level, no test item-related effect was observed on the mortality rate, the clinical signs and behavior in parental generation, the body weight gain and the food consumption. All male and female animals in groups 2, 3, and 4 were noted without any test item related finding at necropsy.

Treatment at 1000 mg/kg was associated with continuing body weight decrease during the study. Mean kidneys weights were statistically significantly increased for male and female. Kidney / body weight ratio were increased 1000 mg/kg Moreover treatment at 1000 mg/kg/day was associated in kidneys with a diffuse tubular degeneration / regeneration in all males.

At 300 mg/kg/day, kidney / body weight ratio were increased at 300 and 1000 mg/kg. These findings may be due to an increased metabolism and excretion of the test item and were therefore considered test item related.

A slightly increased incidence and severity of hyaline droplets in proximal convoluted tubules was noted in males at 1000 and 300 mg/kg.

At 100 mg/kg/day, the test item did not elicit any signs of toxicity.

Consequently, under the experimental conditions, the No Observed Adverse Effect Level (NOAEL) is 100 mg/kg/day and the LOAEL is 300 mg/kg/day for effects on kidney (multifocal tubular degeneration / regeneration in males, and increase in kidney/body weight ratio)