4-tert-butyltoluene

Toxicity to reproduction

Administrative data

Endpoint:

fertility, other

Remarks:

based on test type (migrated information)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

no data

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study.

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

2007

Report date:

2007

Reference 2

Reference Type:

other: abstract

Title:

Unnamed

Year:

2007

Report date:

2007

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 421 (Reproduction / Developmental Toxicity Screening Test)

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

4-tert-butyltoluene

EC Number:

202-675-9

EC Name:

4-tert-butyltoluene

Cas Number:

98-51-1

Molecular formula:

C11H16

IUPAC Name:

1-tert-butyl-4-methylbenzene

Details on test material:

- Name of test material (as cited in study report): p-tert-butyltoluene; supplier: Fuso Chemical Co. Ltd., Osaka, Japan
- Physical state: colourless transparent liquid
- Analytical purity: 96.94%
- Impurities (identity and concentrations): no data
- Lot/batch No.: Lot No. 08008
- Storage condition of test material: room temperature; dark
No further data.

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
male and female Crj:CD(SD)IGS, SPF rats
- Source: Charles River Laboratories, Inc
- Age at study initiation: 8 weeks upon arrival at the testing facility; 10 weeks at the starting day of administration
- Weight at study initiation: 336 - 368 g (males); 221 - 252 (females)
- Fasting period before study: no
- Housing: 5 per cage (during acclimatization), individually after assignment to experimental groups; stainless steel cages; animals were mated in males' cages . Dams were individually housed in a plastic cage with autoclaved beddings from day 18 of gestational period, and were allowed to deliver (spontaneous delivery) and rear the offspring.
- Diet: pellet diet (CRF-1; ORIENTAL YEAST Co., Ltd.), ad libitum
- Water: tap water, ad libitum
- Acclimation period: 5 days quarantine, 7 days acclimatization

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 - 26 °C
- Humidity (%): 40 - 70 %
- Air changes (per hr): 12
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: no data

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
p-tert-Butyltoluene was adjusted by dissolving and diluting it in corn oil. The amount of the test substance was calculated using its purity in preparing the test substance. It is approved that prepared solutions at 0.2, 2, 20, and 200 mg/mL can be kept stable if stored at room temperature under a shaded condition for 7 days. Therefore, the prepared solution at each concentration was stored at room temperature under a shaded condition, and was used within 7 days after preparation. Concentrations of the test substance in administration samples used on the day of start of administration and the day of the termination of administration were measured. The measurement result showed no problems with concentrations of the test substance.

VEHICLE: corn oil
- Justification for use and choice of vehicle (if other than water): no data
- Concentration in vehicle: 0.2, 2, 20, and 200 mg/mL
- Amount of vehicle (if gavage): 5 ml/kg bw

Details on mating procedure:

- M/F ratio per cage: 1/1
- Length of cohabitation: up to 14 days
The animals were continuously housed together during the mating period until copulation was observed. One male in the 50 mg/kg group could not be mated due to the death of the paired female. Therefore, the male rat was not used for mating.
- Proof of pregnancy: vaginal plug and/or sperm in vaginal smear referred to as day 0 of pregnancy

The females that did not achieve successful copulation were sacrificed by exsanguination via the abdominal aorta under ether anesthesia after the termination of mating period and were subsequently necropsied.
No further details.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

males: 50-52 days (males); premating exposure period: 14 days
females: from 14 days prior to mating until day 3 post partum (females); premating exposure period: 14 days

Frequency of treatment:

daily

Details on study schedule:

The administration period for males was total 50 to 52 days including 14 days before mating and subsequent 36 to 38 days (necropsy of males was separately conducted in 3 days since the observation of sperm requires 3 days). The administration period for females was total 41 to 45 days including 14 days before mating, mating period (14 days at the longest), gestational period, and first 3 days in lactation period. The starting day of administration was set as the day 1.

Doses / concentrations

Remarks:

Doses / Concentrations:
1.5, 5, 15, 50 mg/kg bw/d
Basis:
actual ingested

No. of animals per sex per dose:

12 males and 12 females per group

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale:
Dose levels were selected based on two preliminary oral toxicity studies.
First, a single oral dose toxicity test of p-tert-butyltoluene was conducted in rats (dose levels, 0, 250, 500, 1000, and 2000 mg/kg; number of animals, 5 male rats and 5 female rats).
In regard to the results, a pretest was conducted for the preliminary reproduction toxicity screening test of p-tert-butyltoluene by oral administration in rats (dose levels, 0, 125, 250, 500, and 750 mg/kg; number of animals, 5 male rats and 5 female rats; administration period, 14 days). The dose levels of this study were determined based on the results. There were 3 deaths in the 125 mg/kg group and 5 deaths in each of the 250, 500, and 700 mg/kg groups in the pretest for the preliminary reproduction toxicity of p-tert-butyltoluene by oral administration in rats. Further, there were observed decreases in body weight and food consumption and atrophy of the testis and epididymis in the 125 mg/kg group. Therefore, the highest dose level was set to 50 mg/kg that corresponds to an approximately half amount of 125 mg/kg at which dead animals had been observed in the pretest, and lower dose levels were set at 15, 5, and 1.5 mg/kg by a common ratio of approximately 3. The control group was administered with the vehicle (corn oil) alone at the same volume.

Positive control:

no

Examinations

Parental animals: Observations and examinations:

1) MALE RATS
CAGE SIDE OBSERVATIONS and DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Observations about clinical signs and death were conducted twice a day, before and after administration. Necropsy of dead animals was conducted immediately after they were found.

BODY WEIGHT: Yes
- Time schedule for examinations: Body weight was measured twice a week.

FOOD CONSUMPTION: Yes
- Time schedule: Food consumption was measured twice a week during the 14-day period before mating was started and during the period after the termination of mating period.

WATER CONSUMPTION: No

2) FEMALE RATS
CAGE SIDE OBSERVATIONS and DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Observations about clinical signs and death were conducted twice a day, before and after administration. Necropsy of dead animals was conducted immediately after they were found.

BODY WEIGHT: Yes
- Time schedule for examinations: Body weight was measured twice a week during the 14-day period before mating was started and during the mating period, at days 0, 7, 14, and 21 during the gestational period, and at days 0 and 4 in the lactational period.

FOOD CONSUMPTION: Yes
- Time schedule: Food consumption was measured twice a week during the 14-day period before mating was started, at days 2, 9, 16, and 21 during the gestational period, and at day 4 during the lactation period.

WATER CONSUMPTION: No

OTHER:
- Females that did not achieve successful copulation
The females that did not achieve successful copulation were sacrificed by exsanguination via the abdominal aorta under ether anesthesia after the termination of mating period and were subsequently necropsied.

- Observation of Delivery Status
The females with successful copulation were allowed to deliver (spontaneous delivery) their litters. An observation of abnormality of delivery status and checks on completion of delivery were conducted from day 21 of the gestational period to 10 AM on day 25 of the gestational period. If delivery had been completed at 10 AM, the day was set as day 0 of the lactation period.

- Females that did not deliver by 10 AM on day 25 of gestational period
The females that did not deliver by 10 AM on day 25 of the gestational period were sacrificed by exsanguination via the abdominal aorta under ether anesthesia and subsequently necropsied. It was determined whether or not the female was pregnant by examining the presence of implantation.

- Observation of Lactation and Necropsy
An observation of lactation of the dams was conducted every day to day 4 of the lactation period. On day 4 of lactation, dams were sacrificed.

Oestrous cyclicity (parental animals):

An observation of estrous cycle was conducted once a day from the starting day of the administration period to the day at which copulation was observed or to the day of the termination of mating period. In the case that estrus was observed for continuous 2 days, it was counted as one estrus.

Sperm parameters (parental animals):

Parameters examined in all male parental generations:
testis weight, epididymis weight, daily sperm production, sperm count in testes, sperm count in epididymides, enumeration of cauda epididymal sperm reserve, sperm motility, sperm morphology
After sacrifice, the right cauda epididymis was minced in a sperm incubation medium (medium 199 supplemented with 0.5% bovine serum albumin) warmed to 37°C and settled for 5 minutes. Subsequently, sperm stock solution was produced. The examinations on motility, viability, and morphology of sperm were conducted with this sperm stock solution.

Litter observations:

PARAMETERS EXAMINED
The following parameters were examined in F1 offspring:
number and sex of pups, stillbirths, live births, postnatal mortality, presence of gross anomalies, weight gain, physical or behavioural abnormalities

GROSS EXAMINATION OF DEAD PUPS:
yes, for external and internal abnormalities; no further data

- Observation at Delivery
The following data were recorded: number of offspring born, sex ratio, number of stillbirths, number of newborn offspring, and external abnormality.
- Observation of Newborn Offspring
Clinical signs and death were recorded once every day.

- Measurement of Body Weight
Body weight was measured at days 0 (day of birth) and 4 of the lactational period.

Necropsy
The live offspring were sacrificed by exsanguination via the abdominal aorta under ether anesthesia at day 4 of the lactation period and were subsequently necropsied.

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: All surviving animals were sacrificed on days 51 through 53 of the study.
Animals were sacrificed by exsanguination via the abdominal aorta under ether anesthesia and were necropsied at the next day of the last administration (days 51 to 53 of the administration period). The weights of the testis, epididymis and cauda epididymis were measured. The testes and the caput epididymides were fixed in Bouin’s solution for 2 to 3 hours and subsequently refixed in 90% alcohol. The prostate and seminal vesicles were fixed in 20% neutral buffered formalin.
- Maternal animals: All surviving animals were sacrificed on day 4 of lactation.
The dams were sacrificed by exsanguination via the abdominal aorta under ether anesthesia and necropsied at the day that all newborn offspring were dead or at day 4 of the lactation period. The numbers of implantations and pregnant corpora lutea were counted. The weights of ovaries were measured. The ovaries, uterus, and vagina were fixed in 20% neutral buffered formalin.

GROSS NECROPSY
- Gross necropsy consisted of external and internal examinations

HISTOPATHOLOGY / ORGAN WEIGHTS
1) MALE RATS:
Paraffin embedded samples of the testes, caput epididymides, seminal vesicles, and prostate were prepared and evaluated by a conventional method.
HE-stained tissue samples we produced of the testes, caput epididymides, seminal vesicles, and prostate of the animals of the control and 50 mg/kg groups, and histopathological examinations were conducted on the samples. The authors/investigators considered that there was a difference in the number of animals that showed abnormality in the testis and caput epididymis between the 50 mg/kg group and the control group. Therefore, they produced HE-stained tissue samples of these organs of the animals in the 1.5, 5, and 15 mg/kg groups, and conducted the histopathological examinations.
2) MATERNAL RATS
Paraffin embedded samples of the ovaries were prepared using a conventional method. HE-stained tissue sample of the ovaries were prepared from the animals of the control and 50 mg/kg groups and histopathological examinations were conducted.

Postmortem examinations (offspring):

SACRIFICE
- The F1 offspring were sacrificed at 4 days of age.
- These animals were subjected to postmortem examinations (macroscopic and/or microscopic examination) as follows:

GROSS NECROPSY
- Gross necropsy consisted of external and internal examinations; no further data.

HISTOPATHOLOGY / ORGAN WEIGTHS
no data

Statistics:

Due to the maximum size limit of this field, statistical methods are presented in the freetext (Any other information on materials and methods incl. tables)

Reproductive indices:

copulation index,
fertility index,
implantation index,
gestation index,

Offspring viability indices:

delivery index,
birth index,
live birth index,
viability index

Results and discussion

Results: P0 (first parental generation)

Details on results (P0)

1) MALE RATS
CLINICAL SIGNS AND MORTALITY (PARENTAL ANIMALS)
There was a death in the 50 mg/kg group. In the dead case, the animal showed transient salivation, a decrease in locomotor activity, soiled fur, reddish urine, and hypothermia.
In the observation of clinical signs on the live animals, no abnormality was observed in the control group. There was transient salivation in the 1.5 mg/kg group and soiled fur in one animal of the 50 mg/kg group.

BODY WEIGHT AND FOOD CONSUMPTION (PARENTAL ANIMALS)
There were no significant differences in body weight at any day of measurement in the 1.5 and 5 mg/kg groups compared with the control group. There were significant decreases in body weight from day 18 to day 49 of the administration period in the 15 mg/kg group compared with the control group. There were significant decreases in body weight from day 4 to day 49 of the administration period in the 50 mg/kg group compared with the control group. See Fig. 1.
There were no significant differences in food consumption at any day of measurement in the 1.5, 5, and 15 mg/kg groups compared with the control group. There was a significant decrease in food consumption at day 48 of the administration period in the 50 mg/kg group compared with the control group. There was a significant increase in food consumption at day 13 of the administration period in the same group compared with the control group. However, this was a transient change, and was not considered to be attributed to the administration. See Fig. 2.

REPRODUCTIVE FUNCTION: SPERM MEASURES (PARENTAL ANIMALS)
There were no significant differences in sperm motility ratio, path velocity, straight line velocity, curvilinear velocity, beat cross frequency, ratios of morphological abnormality of sperms (ratios of abnormality in the head, tail and the total of those), sperm viability, sperm survivability, sperm count, and sperm count per one gram of the left cauda epididymis in the 1.5 and 5 mg/kg groups, compared with the control group.
There were significant decreases in sperm motility ratio, path velocity, straight line velocity, curvilinear velocity, sperm viability, sperm survivability, sperm count, and sperm count per one gram of the left cauda epididymis in the 15 mg/kg groups compared with the control group. There were significant increases in beat cross frequency and ratios of morphological abnormality of sperms (ratios of abnormality in the head, tail and the total of those) in the same group.
There were significant decreases in sperm motility ratio, sperm count, sperm count per one gram of the cauda epididymis in the 50 mg/kg group compared with the control group. Among the animals with low numbers of motile sperms, there was only one animal that could be used for measurements of path velocity, straight line velocity, curvilinear velocity, beat cross frequency, sperm viability, and sperm survivability. However, there were decreases in all the parameters. The authors could conduct the observation of sperm morphology on only 5 animals in the 50 mg/kg group. However, there were significant increases in the ratios of morphological abnormality of sperms (ratios of abnormality in the head, tail and the total of those). See Table 2.

ORGAN WEIGHTS (PARENTAL ANIMALS)
There was no significant difference in the body weight at the day of necropsy in the 1.5 and 5 mg/kg groups compared with the control group. There were significant decreases in body weight at the day of necropsy in the 15 and 50 mg/kg groups compared with the control group.
In the organ weight measurement, there were no significant differences in absolute and relative weights of the testis and epididymis in the 1.5 and 5 mg/kg groups compared with the control group. There were significant decreases in absolute weight of the epididymis and a decreasing tendency of absolute weight of the testis in the 15 mg/kg group compared with the control group. There were significant decreases in absolute and relative weights of the testis and epididymis in the 50 mg/kg group compared with the control group. See Table 1.

GROSS PATHOLOGY (PARENTAL ANIMALS)
In the live animals, there was no abnormality in the control, 1.5, and 5 mg/kg groups. There was atrophy of the testes and the epididymides in one animal of the 15 mg/kg group. There was atrophy of the testes and the epididymides in all 11 animals of the 50 mg/kg group.
There was atrophy of the thymus, ulcer on the anterior gastric mucosa, and atrophy of the testes, epididymides, seminal vesicles, and prostate in the dead animals of the 50 mg/kg group.

HISTOPATHOLOGY (PARENTAL ANIMALS)
Testis: There was no abnormality in the control, 1.5, and 5 mg/kg groups. There was atrophy of the seminiferous tubules in 4 animals, hyperplasia of Leydig Cells in 2 animals, and remaining spermatids at step 19 in the seminiferous tubules of groups 3 and 4 in one animal of the 15 mg/kg group. There was atrophy of the seminiferous tubules and hyperplasia of Leydig cells in 11 animals in the 50 mg/kg group.
Epididymis (Caput Epididymis): There was no abnormality in the control, 1.5, and 5 mg/kg groups. There was a decrease in sperm count in 4 animals in the 15 mg/kg group. There was a decrease in sperm count in 11 animals in the 50 mg/kg group.
There was atrophy of the seminiferous tubules in the testis and a decrease in sperm count in the epididymis in the 15 and 50 mg/kg group. In addition, there was hyperplasia of Leydig cells in the testis in the 50 mg/kg group. Significant differences were observed with all these changes compared with the control group. However, the remaining spermatids in the seminiferous tubules of groups 3 and 4 were observed in only one animal of the 15 mg/kg group. Further, this change was not observed in the 50 mg/kg group. Therefore, this change is considered to be an accidental case.
Besides, there was lymphoid cell infiltration in the prostate. However, it was determined that this was an accidental change. See Table 3.


2) FEMALE RATS
CLINICAL SIGNS AND MORTALITY (PARENTAL ANIMALS)
There were one death in the 15 mg/kg group and 6 deaths in the 50 mg/kg group. There was hypothermia and a decrease in locomotor activity, and transient salivation in the 15 mg/kg group. There was hypothermia, prone position, a decrease in locomotor activity, piloerection, soiled fur, bradypnea, and transient salivation in the 50 mg/kg group.
In the observation of clinical signs on the living animals, there was no abnormality in the control, 1.5, and 5 mg/kg groups. There was transient salivation in the 15 mg/kg group. There was transient salivation, hypothermia, a decrease in locomotor activity, staggering gait, lacrimation, diarrhea, and muscle relaxation in the 50 mg/kg group.

BODY WEIGHT AND FOOD CONSUMPTION (PARENTAL ANIMALS)
There was no significant difference in body weight at any day of measurement in the 1.5, 5, and 15 mg/kg groups before mating was started, compared with the control group. There were significant decreases in body weight from day 4 to day 15 of the administration period in the 50 mg/kg group compared with the control group.
There was no significant difference in body weight at any day of measurement during the gestational period in the 1.5 mg/kg group, compared with the control group. There were significant decreases in body weight at days 7 and 14 of the gestational period in the 5 mg/kg group compared with the control group. There were significant decreases in body weight from day 7 to day 21 of the gestational period in the 15 mg/kg group compared with the control group.
There was no significant difference in body weight at any day of measurement during the lactation period in the 1.5 mg/kg group, compared with the control group. There was a significant decrease in body weight at day 4 of the lactation period in the 5 mg/kg group compared with the control group. There was a decreasing tendency of body weight in one animal of the 15 mg/kg group at day 4 of the lactation period. See Fig. 3.
There was no significant difference in food consumption at any day of measurement before mating was started in the 1.5 and 5 mg/kg groups, compared with the control group. There were significant increases in food consumption at day 6 of the administration period in the 15 and 50 mg/kg groups compared with the control group. However, these were transient changes, and were not considered to be a toxicological effect.
There was no significant difference in food consumption at any day of measurement during the gestational period in the 1.5, 5, and 15 mg/kg groups, compared with the control group.
There was no significant difference in food consumption in the 1.5 mg/kg group during the lactation period, compared with the control group. There was a significant decrease in food consumption at day 4 of the lactation period in the 5 mg/kg group compared with the control group. There was a decreasing tendency of food consumption in one animal of the 15 mg/kg group at day 4 of the lactation period. See Fig.4.

REPRODUCTIVE FUNCTION: ESTROUS CYCLE (PARENTAL ANIMALS)
No changes attributable to administration of the test substance were noted in the numbers of estrous cases.

ORGAN WEIGHTS (PARENTAL ANIMALS)
There was no significant difference in the body weight at the day of necropsy in the 1.5 mg/kg group compared with the control group. There were significant decreases in body weight at the day of necropsy in the 5, 15, and 50 mg/kg groups compared with the control group.
In the organ weight measurement, there were no significant differences in absolute and relative weights of the ovary in the 1.5, 5, 15 and 50 mg/kg groups compared with the control group. See Table 4.

GROSS PATHOLOGY (PARENTAL ANIMALS)
There was no abnormality in the live animals of any group.
Among the dead animals, there was a dark red spot on the glandular gastric mucosa in one animal of the 15 mg/kg group. There was pale coloor of the liver in one animal and atrophy of the thymus in one animal of the 50 mg/kg group. All the 3 animals that died after copulation were infertile.

HISTOPATHOLOGY (PARENTAL ANIMALS)
Ovary: there was no abnormality in the control and 50 mg/kg groups.



REPRODUCTIVE PERFORMANCE (PARENTAL ANIMALS); MALES AND FEMALES
(1) Frequency of Estrus, Copulation Index, and Fertility Index
There was no significant difference in frequency of estrus during the administration period (14 days) before mating between each group and the control group.
There was no significant difference in days required for copulation between each group and the control group.
One pair of animals did not achieve copulation in the 50 mg/kg group. There was no significant difference in copulation index between each group and the control group.
There were 8 non-pregnant females in the 15 mg/kg group. There was no pregnant female in the 50 mg/kg group. There were significant decreases in fertility index in the 15 and 50 mg/kg group compared with the control group. See Table 5.

(2) Gestational Period, Delivery Status, Number of Pregnant Corpora Lutea, Implantation Index, and Gestation Index
There was no significant difference in gestational period in the 1.5, 5, and 15 mg/kg groups compared with the control group.
There was no abnormality of delivery status in the control, 1.5, and 5 mg/kg groups. No newborn offspring were obtained with one dam of the 15 mg/kg group since the litters were all dead.
There were no significant differences in number of pregnant corpora lutea, number of implantations, and implantation index in the 1.5, 5, and 15 mg/kg groups compared with the control group.
The gestation index was 100% in the 1.5 and 5 mg/kg groups. The gestation index of the 15 mg/kg group was 66.7% since one dam did not deliver live offspring.
In the observation of lactation status, there was no abnormality in the control, 1.5, and 5 mg/kg groups. All newborn pups of one dam of in the 15 mg/kg group died by day 1 of the lactation period. See Table 6.

(3) Delivery Index and Live Birth Index
There was no significant difference in number of offspring born, number of stillbirths, number of newborn offspring at day 0 of the lactation period, sex ratio, delivery index, birth index, and live birth index in the 1.5 and 5 mg/kg groups, compared with the control group. There were significant decreases in number of offspring born and number of newborn offspring at day 0 of the lactation period, decreasing tendency of delivery index, birth index, and live birth index, and an increase in number of stillbirths in the 15 mg/kg group, compared with the control group. See Table 6.

Effect levels (P0)

1

Dose descriptor:

NOEL

Effect level:

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

Sex:

male

Basis for effect level:

other: NOEL for repeated dose toxicity

2

Dose descriptor:

NOEL

Effect level:

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

Sex:

female

Basis for effect level:

other: NOEL for repeated dose toxicity

3

Dose descriptor:

NOEL

Effect level:

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

Sex:

male/female

Basis for effect level:

other: NOEL for reproductive performance

Results: F1 generation

Details on results (F1)

VIABILITY and CLINICAL SIGNS (OFFSPRING)
There were no significant differences in number of live offspring at day 4 of the lactation period and viability index at day 4 of the lactation period in the 1.5 and 5 mg/kg group compared with the control group. The newborn offspring of one dam died by day 1 of the lactation period in the 15 mg/kg group, and there were decreasing tendencies of number of live offspring at day 4 of the lactational period and viability index at day 4 of the lactation period.
There was no abnormality in the observation of external abnormality of newborn offspring in any group. In the observation of clinical signs on the newborn offspring.
There was no abnormality in the control, 5, and 15 mg/kg groups. There was necrosis of the tail in one offspring of the 1.5 mg/kg group. However, this is considered to be an accidental case.
See Table 6.

BODY WEIGHT (OFFSPRING)
There were no significant difference in body weights of males and females at days 0 and 4 of the lactation period compared with the control group. There were significant decreases in body weights of males and females at days 0 and 4 of the lactation period in the 5 mg/kg group compared with the control group. There were decreasing tendencies of body weights of males and females at days 0 and 4 of the lactation period in the 15 mg/kg group compared with the control group. See Table 6.

NECROPSY OF OFFSPRING
There was no abnormality in the control, 5, and 15 mg/kg groups. There was necrosis of the tail in one male in the 1.5 mg/kg group in the observation of clinical signs. However, there was no significant difference compared with the control group. This change was not attributed to the dose level.

Effect levels (F1)

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

1.5 mg/kg bw/day

Sex:

male/female

Basis for effect level:

other: NOAEL for effects on F1 offspring

Overall reproductive toxicity

Reproductive effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

According to the authors, the NOELs for repeated dose toxicity are considered to be 5 mg/kg bw/d for males and 1.5 mg/kg bw/d for females.
The NOELs for reproductive performance are considered to be at 5 mg/kg bw/d for both sexes.
The NOEL for pups is considered to be at 1.5 mg/kg/day.