O,O,O-tris(2(or 4)-C9-10-isoalkylphenyl) phosphorothioate

Toxicity to reproduction

Administrative data

Endpoint:

screening for reproductive / developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2011

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2011

Report date:

2011

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 421 (Reproduction / Developmental Toxicity Screening Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

A mixture of: triphenylthiophosphate and tertiary butylated phenyl derivatives

EC Number:

421-820-9

EC Name:

A mixture of: triphenylthiophosphate and tertiary butylated phenyl derivatives

Cas Number:

192268-65-8

Molecular formula:

Unspecified

IUPAC Name:

reaction mass of: triphenylthiophosphate and tertiary butylated phenyl derivatives

Details on test material:

- Physical state, appearance: Liquid, colorless, clear
- Storage conditions: Room temperature

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: room temperature

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Laboratories, B.V., 5961 NM Horst / Netherlands
- Age at study initiation: 11 weeks
- Weight at study initiation: Males: 303 to 335 g; Females: 196 to 222 g
- Fasting period before study: none
- Housing: Single cages
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3 °C
- Humidity (%): 30 – 70%
- Air changes (per hr): 10 – 15
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 14-Apr-2011 To: 02-Jun-2011

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

polyethylene glycol

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The substance was weighed into a brown glass beaker on a tared precision balance and approximately 80% of the vehicle was added (w/v). Using an appropriate homogenizer, a homogeneous suspension was prepared. Having obtained a homogeneous mixture, the remaining vehicle was added. Separate formulations were prepared for each concentration.

VEHICLE
- Amount of vehicle (if gavage): 4 mL/kg body weight

Details on mating procedure:

- M/F ratio per cage: 1:1
- Length of cohabitation: 11 days
- Proof of pregnancy: daily vaginal smear was sperm positive or a copulation plug was observed
- Further matings after two unsuccessful attempts: not needed
- After successful mating each pregnant female was caged in single cages

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

On the first treatment day samples from the control group as well as three samples (top, middle and bottom) of about 2 g of each concentration were taken prior to dosing for analysis of concentration and homogeneity. Samples of about 2 g of each concentration were taken from the middle only to confirm stability (2, 4 hrs and 48 hrs). During the second last week of the treatment, samples were taken from the middle to confirm concentration. The aliquots for analysis of dose formulations were frozen (-20 ± 5 °C) and delivered on dry ice and stored there at -20 ± 5 °C until analysis.
The samples were analyzed by analytical procedure provided by the Sponsor and adapted at at the CRO. The test item was used as the analytical standard.

Duration of treatment / exposure:

Males: Minimum 4 weeks
Females: Approximately 7 weeks

Frequency of treatment:

daily

Details on study schedule:

not applicable for screening study

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

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

Doses / concentrations 2

Dose / conc.:

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

Doses / concentrations 3

Dose / conc.:

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

Doses / concentrations 4

Dose / conc.:

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

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The dose levels were selected based on a 28-day oral toxicity study in which the NOAEL was established at 200 mg/kg body weight/day.

Positive control:

not required

Examinations

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily cage-side clinical observations (once daily, during acclimatization and up to day of necropsy). Viability/mortality was checked twice daily.
Additionally females were observed for signs of difficult or prolonged parturition, and behavioral abnormalities in nesting and nursing.

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: Recorded daily from treatment start to day of necropsy.

OTHER:
For males: Food consumption: Weekly during pre-pairing and after pairing periods.
For females: Pre-pairing period days 1 - 8 and 8 - 14, gestation period days 0 - 7, 7 - 14 and 14 - 21 post coitum and lactation period days 1 - 4 post partum.

Oestrous cyclicity (parental animals):

no data

Sperm parameters (parental animals):

Parameters examined in male parental generations:
testis weight, epididymis weight, completeness of stages or cell populations of the testes

Litter observations:

PARAMETERS EXAMINED
The following parameters were examined in 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 abnormalities

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: All surviving animals (day 28)
- Maternal animals: All surviving animals (post partum day 4)

GROSS NECROPSY
- For the parent animals, special attention was directed at the organs of the reproductive system. The number of implantation sites and corpora lutea were recorded for all dams with litters. The uteri of non-pregnant females were placed in a solution of ammonium sulfide to visualize possible hemorrhagic areas of implantation sites

HISTOPATHOLOGY / ORGAN WEIGHTS
The ovaries from all parental females were preserved in neutral phosphate buffered 4% formaldehyde solution.
The testes and epididymides from all parental males were preserved in Bouin’s fixative. The prostate and seminal vesicles from all males were fixed in neutral phosphate buffered 4% formaldehyde solution. Special emphasis was made on the stages of spermatogenesis and histopathology of interstitial cell structure.

Organ weights: testes and epididymides

Histological examination of ovaries was carried out in female no. 55 that did not give birth. In addition, microscopic examination of the reproductive organs of the infertile male no. 15 was made.

Postmortem examinations (offspring):

SACRIFICE
- The offspring was sacrificed on day 4 post partum.

Statistics:

Means and standard deviations of various data were calculated.
• The Dunnett-test (many to one t-test) based on a pooled variance estimate was applied if the variables could be assumed to follow a normal distribution for the comparison of the treated groups and the control groups for each sex.
• The Steel-test (many-one rank test) was applied instead of the Dunnett-test when the data could not be assumed to follow a normal distribution.
• Fisher's exact-test was applied if the variables could be dichotomized without loss of information.

Reproductive indices:

fertility, conception and gestation indeces

Offspring viability indices:

viability indices (day 0-4)

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Signs of discomfort such as salivation and pushing the head through the bedding material were observed at 50 and/or 250 mg/kg in males and females over the study. At 10 mg/kg body weight/day, no test item-related clinical signs were observed during the study. The only observation was hair loss on the dorsal side of the neck in female no. 60 starting on day 20 of the gestation until the termination. In control group, one male was noted to have a wound on the dorsal side of the neck at termination.

Dermal irritation (if dermal study):

not examined

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

No test item-related adverse effects were observed in mean body weight and mean body weight gain of males at all dose levels. At 50 and 250 mg/kg body weight/day, the statistically significantly higher mean body weight gain during the pre-pairing and pairing periods, were considered to be incidental and not indicative of any test item effect. In females, at 250 mg/kg body weight/day, mean body weight gain was statistically significantly lower on days 2, 6 and 14 of the pre-pairing period and between days 1 and 4 and on day 12 of the gestation period. These were effecs of the treatment with the test item, which did not affect the mean body weight, therefore not considered to be adverse. At 50 mg/kg body weight/day, mean body weight gain was statistically significantly lower on days 3 and 11 of the pre-pairing period and on days 1 and 2 of the gestation period. These were
transient fluctuations, which did not affect mean body weight and therefore considered not to be adverse.
At 10 mg/kg body weight/day, no test item-related effects were observed during the study.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

No test item-related effects were observed in mean food consumption of males at all dose levels during the whole study. At 250 mg/kg body weight/day, during the pre-pairing period mean food consumption was statistically significantly lower during the first week of the pre-pairing period (-11.8% compared to the control) and slightly lower during the second week. This was a transient reduction and considered not to be adverse as, mean food consumption recovered and was similar to the control group during the gestation and lactation periods. At 10 and 50 mg/kg body weight/day, no test item-related effects were observed in mean food consumption.

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

All findings recorded were within the range of normal background lesions, which may be recorded in animals of this strain and age. And also, no test item-related histological finding was recorded in ovary of one female (no. 55) that did not give birth and in reproductive organs of one infertile male (no. 15). No differences on the completeness of stages or cell populations of the testes were recorded between controls and high dose animals.

Histopathological findings: neoplastic:

not examined

Other effects:

no effects observed

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

no effects observed

Description (incidence and severity):

The median and mean precoital times were unaffected by treatment with the test item. Mean precoital times were 2.6, 3.4, 2.0 and 2.9 days in order of ascending dose level. The median precoital time was 3, 3, 1 and 3 days in order of ascending dose level. One female (no. 55) at 10 mg/kg body weight/day was not pregnant. Thus, the fertility indices were: 100.0%, 90.0%, 100.0% and 100.0% in ascending of dose level and gave no indication of any test item-related effect. The mean duration of gestation was unaffected by treatment with the test item. Mean number of corpora lutea (determined at necropsy) was 14.0, 15.2, 13.5 and 13.3 in order of ascending dose level and gave no indication of a test item-related effect. The mean number of implantations per dam was unaffected by treatment with the test item. As the higher incidence of post-implantation loss which occurred at 250 mg/kg body weight/day (8.9% versus 5.1%) was within the range of the historical control data was not considered to be adverse. The mean number of implantations per dam were: 13.7, 14.6, 11.6 and 12.3 in order of ascending dose level. The mean incidence of post-implantation loss as a percentage of total implantations was: 5.1%, 1.5%, 0.9% and 8.9% in order of ascending dose level.

Effect levels (P0)

1

Key result

Dose descriptor:

NOEL

Effect level:

>= 250 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: fertility index, viability index

2

Key result

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Based on the lower food consumption and the occasional lower mean body weight gain which were not considered to be adverse in females at 250 and 50 mg/kg body weight/day.

Target system / organ toxicity (P0)

Key result

Critical effects observed:

no

Results: F1 generation

General toxicity (F1)

Clinical signs:

no effects observed

Description (incidence and severity):

At first litter check, the findings noted were: tail reduced in size in male pup at 10 mg/kg body weight/day, wound on snout in one male pup at 50 mg/kg body weight/day and in one female at 250 mg/kg body weight/day and tail missing in one male pup at 250 mg/kg body weight/day. Type and incidences of these findings did not give any indication of any test item-related effect.

Dermal irritation (if dermal study):

not examined

Mortality / viability:

no mortality observed

Description (incidence and severity):

The number of live pups at first litter check was unaffected by treatment with the test item. The mean number of live pups per litter was: 13.0, 14.3, 11.5 and 11.2 in order of ascending dose level.
At 10 mg/kg body weight/day, one female pup was found dead on day 2 post partum and at 50 mg/kg body weight/day one female pup was missing on day 4 post partum. The resulting viability indices were: 100.0%, 99.2%, 99.1% and 100.0% in order of ascending dose levels.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

Mean pup weights on day 1 post partum and mean pup weight development during the lactation to day 4 post partum were unaffected by treatment with the test item. Mean pup weights on day 4 post partum were 9.0, 8.3, 9.2 and 9.0 g for combined data of male and female pups in order of ascending dose level.

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Sexual maturation:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

no effects observed

Description (incidence and severity):

No abnormal findings were noted at macroscopic examination of the pups.

Histopathological findings:

not examined

Other effects:

no effects observed

Description (incidence and severity):

Sex ratios at first litter check and on day 4 post partum were unaffected by exposure to the test item. The proportion of males on day 4 post partum was 49%, 52%, 52% and 58% in order of ascending dose level.

Effect levels (F1)

Key result

Dose descriptor:

NOEL

Generation:

F1

Effect level:

>= 250 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Absence of adverse findings, with sacrifice on day 4 post partum.

Target system / organ toxicity (F1)

Key result

Critical effects observed:

no

Overall reproductive toxicity

Key result

Reproductive effects observed:

no

Applicant's summary and conclusion

Conclusions:

Under the conditions of this study, the NOEL (No Observed Effect Level) for reproduction/ developmental toxicity was considered to be 250 mg/kg body weight/day.

Executive summary:

In a GLP-compliant reproduction screening study following OECD guideline 421, four groups of 10 males and 10 females were treated by gavage with the test item once daily. Males were treated over a 14-day pre-pairing period and during the pairing period up to one day before necropsy. Females were treated throughout the pre-pairing, pairing, gestation and lactation period up to day 4 post partum. The following dose levels were used: Group 1: 0 mg/kg body weight/day (control group); Group 2: 10 mg/kg body weight/day; Group 3: 50 mg/kg body weight/day; Group 4: 250 mg/kg body weight/day; A standard dose volume of 4 mL/kg body weight with a daily adjustment to the actual body weight was used. Control animals were dosed with the vehicle alone (highly purified water). All animals survived until the scheduled necropsy. Signs of discomfort such as salivation at dose level of 50 and 250 mg/kg body weight/day and pushing the head through the bedding material at dose level of 250 mg/kg body weight/day were observed during the course of the study. No test item-related effects were observed in mean food consumption of males during the entire study at all dose levels. At 250 mg/kg body weight/day, mean food consumption was statistically significantly lower in females during the first week of the pre-pairing period, thereafter it progressively recovered, and therefore it was not considered to be adverse. No test item-related effects were observed in mean body weight and mean body weight gain of males at all dose levels during the entire study. In females, at 250 mg/kg body weight/day, mean body weight gain was statistically significantly lower on three occasions during the pre-pairing period and at the beginning of the gestation. This was considered an effect of the test item but not to be adverse as mean body weight was not affected. At 50 mg/kg body weight/day, the occasional lower body weight gain observed during the study was not indicative of any test item-related effect. Mating performance, fertility, conception and gestation indeces were not affected by treatment with the test item. The mean duration of gestation was also unaffected by treatment with the test item. The mean number of corpora lutea, the mean number of implantations per dam, and the incidence of post-implantation losses were not affected by treatment with the test item. No test item-related effects were observed in mean values of absolute and relative weight of testes and epididymides. There was no histological evidence of toxicological properties in the organs and tissues examined. No differences on the completeness of stages or cell populations of the testes were recorded between controls and high dose animals. The number of live pups at first litter check and on day 4 post partum was unaffected by the treatment with the test item. No test item-related clinical signs were observed at first litter check and during the lactation. Mean pup weights and weight development were also not affected by the treatment with the test item. Taking into account the lower food consumption and the occasional lower mean body weight gain which were not considered to be adverse in females at 250 and 50 mg/kg body weight/day, the general NOAEL (No Observed Adverse Effect level) was established at 250 mg/kg body weight/day for both males and females. Under the conditions of this study, the NOEL (No Observed Effect Level) for reproduction/ developmental toxicity was considered to be 250 mg/kg body weight/day.