2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study, but outdated version of guideline (treatment only up to gestation day 15), GLP study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1987

Report date:

1987

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Version / remarks:

(adopted May 1981)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol

EC Number:

274-570-6

EC Name:

2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol

Cas Number:

70321-86-7

Molecular formula:

C30H29N3O

IUPAC Name:

2-(2H-1,2,3-benzotriazol-2-yl)-4,6-bis(2-phenylpropan-2-yl)phenol

Test material form:

solid: particulate/powder

Details on test material:

- Physical state: white powder
- Analytical purity: commercial grade
- Storage condition of test material: room temperature
- Solubility: practically insoluble in water

Specific details on test material used for the study:

- Analytical purity: 99.7%
- Batch No.: EN 02885.32 (commercial grade)
- Physical state: solid
- Storage: room temperature
- Solubility in water: insoluble

Test animals

Species:

rat

Strain:

other: RAIf (SPF),

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Further characterisation: hybrids of RII/1 x RII/2
- Source: Animal Production, WST 455, Ciba Geigy Ltd., Stein, Switzerland
- Age at study initiation: about 2 months
- Weight at study initiation: 180 g - 200 g
- Housing: groups of 4 in macrolon cages with a wire mesh top and with standardised granulated soft wood
- Diet: pelleted, certified standard diet (Nafag No. 890 Tox); ad libitum
- Water: tap water; ad libitum
- Acclimation period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 ± 1
- Humidity (%): 55 ± 15
- Air changes (per hr): about 16
- Photoperiod (hrs dark / hrs light): 12/12

All batches of diet were assayed for composition and contaminant levels by the manufacturer. The drinking water quality fulfilled the specifications of the "Schweizerisches Lebensmittelbuch" (1972).

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

polyethylene glycol

Remarks:

(50% in water)

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The suspensions of the test material were freshly prepared daily and the homogeneity of the suspensions was maintained by means of a magnetic stirrer. The suspensions prepared contained 0, 30, 100 and 300 mg/mL of the test material.

VEHICLE
- Concentration in vehicle: 1:1 mixture of distilled water and polyethylene glycol 400
- Amount of vehicle: 10 mL/kg
- Purity: polyethylene glycol 400 (practical grade, Fluka AG, Switzerland)

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The content analysis of the test article suspensions showed values ranging from 93.5 to 100.8 % of the nominal values.

Details on mating procedure:

- Impregnation procedure: cohoused
- M/F ratio per cage: 1/3
- Length of cohabitation: 4-6 h
- Proof of pregnancy: vaginal plug / sperm in vaginal smear referred to as day 0 of pregnancy

Duration of treatment / exposure:

from day 6 to day 15 of the pregnancy

Frequency of treatment:

daily

Duration of test:

21 days

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 300, 1,000 and 3,000 mg/kg bw (higher concentrations were technically not feasible)
Basis:
actual ingested

No. of animals per sex per dose:

24 per group at study initiation

Control animals:

yes, concurrent vehicle

Details on study design:

Dose selection rationale:
The dose levels were selected on the basis of a previously conducted preliminary teratogenicity study. Groups of each 12 pregnant rats were treated with 0, 1,000 mg/kg and 3,000 mg/kg body weight from day 6 until day 15 of pregnancy with the test substance.

The females of both the experimental groups remained unaffected by the treatment. Food consumption, body weight development, general health and all litter parameters were comparable to those of the control group. One female of the control group died on day 20 post coitum: Necropsy revealed bloody liquid in the uterus. One malformation was found amongst the fetuses of the control group (cleft palate in combination with maldeveloped tongue). Based on the foregoing results, it was decided that the high dose should be 3000 mg/kg, the indermediate dose 1000 mg/kg and the low dose 3,000 mg/kg, a dose expected to yield a no-effect level.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations: daily

FOOD CONSUMPTION AND COMPOUND INTAKE: Yes
- Time schedule: days 6, 11, 16 and 21 of pregnancy
- Food consumption for each animal determined and mean daily diet consumption calculated as g food per period/ days per period x no. of animals per cage: Yes

WATER CONSUMPTION AND COMPOUND INTAKE: No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 21
- Organs examined: main organs of the thoracic and abdominal cavities, in particular the genitals; number of corpora lutea in each ovary, weight of the uterus including contents, uterine contents

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included: number and location of live and dead fetuses in the uterine horns, number and location intrauterine resorption sites (early/late),
- early embryonal resorptions: implantation sites without placenta
- late embryonal/fetal resorptions: implantation sites with placenta
- abortions: "empty" implantation sites with white or yellow stained nodules in the uterus horn visible from the outside

Uterine horns showing no implantation sites were placed into an aqueous solution of ammonium sulfide to visualize possible haemorrhagic alterations of such sites.

Fetal examinations:

- Sex determination: Yes (ano- genital distance criteria)
- Careful external (gross) examinations: Yes (live fetuses): extremities or parts thereof, tail, trunk, head (brain, eyes, pinnae, jaws, oral orifice cleft lip/jaw/palate), all body regions
- Body weight determination: Yes
- Visceral examinations: Yes (one third of the fetuses per litter): skin, central nervous system (brain, spinal cord, eyes), body cavities (pericardial cavity, pleural cavity, diaphragm), respiratory system (nasal cavity, nasal septum, choanae, trachea, bronchi, lungs), digestive system (oral cavity, palate, tongue, oesophagus, stomach, intestine, rectum, liver), endocrine system (thyreoidea, pancreas, adrenals, thymus), circulatory system (spleen, heart, major vessels), excretory system (kidneys, ureters, ruinary bladder), genital system (testes, epididymides, deferent ducts, seminal vesicles, ovaries, oviducts, uterus)
- Skeletal examinations: Yes (two thirds of the fetuses per litter): cranial skeleton (nasals, frontals, parietals, interparietals, supraoccipital, exoccipitals), axial skeleton (vertebrae, ribs, sternebrae), appendicular skeleton (shoulder girdle, pelvic girdle, upper and lower extremities)

Statistics:

All values were analysed by the Student's t-test, except for the analysis of fetal anomalities, which were analysed by the CHI-square test.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:no effects

Details on maternal toxic effects:
- Clinical signs: A few animals, such as two from the control group, five from the low-dose group and one from each the intermediate and high dose groups developed some necrotic areas on the skin which were not considered to be due to the treatment.
- Mortality: No mortality occurred during treatment or post-treatment period.
- Body weight: Body weight and corrected body weights were comparable for all groups over the study period (see table 1). In the intermediate dose group body weight change was superior to that of the control group during days 6 through 11 of pregnancy (significant difference confirmed by Student's t-test, p < 0.05). No other differences and no treatment-related changes were observed.
- Food consumption: Food consumption was not adversely influenced for all the three dose groups in comparison to controls. Neither in the pre-gestation phase (d0 - d6) (19.42 g, 19.50 g and 19.72 g versus 19.07 g in controls) nor during gestation (d6 - d21) (24.85 g, 24.49 g and 25.09 g versus 23.61 g in controls).
- Macroscopic findings: No changes were recorded which might be related to the treatment with the test substance.

Maternal postmortem examination:
- 0 mg/kg bw: 2 females bore no implantation sites and 1 female had a dead foetus. All three animals were excluded from the calculation of means.
- 300 mg/kg bw: no effects detected
- 1000 mg/kg bw: 1 female with partial abortion, mean number of corpora lutea and implantation sites was slightly but not significantly increased
- 3000 mg/kg bw: 1 female with partial abortion, 1 female with haemorrhagic changes of the uterine epithelium, 1 female with no left uterus horn, mean number of corpora lutea was slightly but not significantly increased while the mean number of implantation sites was slightly decreased (no statistical significance). This implies the preimplantation loss was higher in comparison to controls. For one female of the high dose group, premature birth of three foetuses was observed on day 21 post coitum. Since body weight and uterus weight could not be determined on the day of expected delivery (day 21 p.c), this female was excluded from calculation of the corresponding means. The animal was considered, however, for means concerning pregnancy and fetal data.

Effect levels (maternal animals)

Dose descriptor:

NOAEL

Effect level:

3 000 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: other:

Maternal abnormalities

Abnormalities:

no effects observed

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
The rates of embryo and foetal lethality (resorptions indicating post-implantation loss) were found to be similar for all groups. One dead fetus was found amongst a litter of the high-dose group. The uterine contents of a female from the control group consisted of one dead fetus only. In the high-dose group the mean litter size showed a slight but statistically not significant reduction and remained unchanged in the low and intermediate dose groups. The average number of male and female foetuses per litter was similar for all groups. The male-to-female sex ratios were comparable for all groups in this study. The average body weight of the live foetuses was not significantly altered in the experimental groups on the per litter basis. However, comparing the mean foetal body weights per group, a significant reduction of the average female body weight in the low dose group (t-test, p < 0.05) and of the average male and average female and overall average weight of the intermediate dose group (p < 0.05) was observed. The latter findings were not assumed to be of experimental significance.

Gross malfomations upon external examination were found in 1 male of the control group which exhibited a generalised oedema and in one female of the high dose group which exhibited omphalocele. No gross malformations were observed in the low and intermediate dose groups. No visceral malformations or anomalies were detected in any group on about one third of live fetuses per litter. The incidence of skeletal anomalies was comparable between treated groups and the control group (4, 2 and 6 versus 4 in controls, for 300, 1,000, 3,000 mg/kg bw). Most of these anomalies were consistent irregular ossification of sternebrae (sternebrae 1 and/or 6 and 2).

Effect levels (fetuses)

Dose descriptor:

NOEL

Effect level:

3 000 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no adverse effects observed

Fetal abnormalities

Abnormalities:

no effects observed

Overall developmental toxicity

Developmental effects observed:

no

Any other information on results incl. tables

Table 1: Body weight

	Dose (mg/kg bw)
	0	300	1000	3000
No. pregnant females	22	24	24	24
day	Mean body weight (g)
0	194.1	194.9	197.2	196.5
21	365.1	368.8	368.3	362.5
	Mean body weight changes (g)
0-6	32.9	32.0	31.0	32.8
6-11	27.3	29.4	30.5	30.1
11-16	45.0	42.5	41.8	39.8
16-21	66.0	70.0	67.8	63.3
0-21	171.0	173.9	171.1	166.0
6-21	138.3	142.0	140.1	133.2
6-16	72.3	71.9	72.3	69.9
Gravid uterus weight (g)	113	108	111	103
Corrected body weight (g)*	252	261	258	260
Corrected body weight gain (g) **	26	34	29	30
Corrected body weight gain (%)***	11	15	13	13

* "corrected" body weight is the difference of the body weight (day 21) minus the uterus weight

** "corrected" body weight (day 21) minus body weight (day 6)

*** "corr." body-weight gain divided by the body weight (day 6), times 100

Table 2: Summary of results

	Dose (mg/kg bw)
	0	300	1000	3000
Number of females mated	24	24	24	24
Number pregnant females	22 (91.7%)	24 (100%)	24 (100%)	24 (100%)
Dams with live foetuses	21 (87.5%)	24 (100%)	24 (100%)	23 (100%)*
Dams with partial resorptions	9 (37.5%)	15 (62.5%)	13 (54.2%)	14 (58.3%)
Dams with partial abortion	0 (0%)	0 (0%)	1 (4.2%)	1 (4.2%)
Corpora lutea (mean)	16.1	16.0	16.9	16.9
Implantation sites (mean)	15.3	15.2	16.0	14.3
Pre-implantation loss (%)**	6.6	5.7	7.6	15.0
Implantation efficiency (%)	93.4	94.3	92.4	85
Early resorptions = embryonic resorptions (mean/total/(%)***)	0.48/10/(3.1%)	0.88/21/(5.8%)	0.96/23/(6.0%)	0.87/20/(6.1%)
Late resorptions = foetal resorptions (mean/total/(%)***)	0.05/1/(0.3%)	0	0.04/1/(0.3%)	0.08/2/(0.6%)
Total resorptions (mean/total/(%)***)	0.52/11/(3.4%)	0.88/21/(5.8%)	1.00/24/(6.3%)	0.96/22/(6.7%)
Litters evaluated	21	24	24	23
Number live foetuses	311	344	359	306
Foetal viability %	100	100	100	99.7
Litter weight (g)	81.8	78.4	79.9	72.6
Sex-ratio (m/f), per litter	0.46	0.49	0.46	0.5
Sex-ratio (m/f), per group	0.46	0.48	0.46	0.51
Mean body weight per group (g)	5.5	5.5	5.3 (p< 0.05)	5.5
Foetuses with gross malfunction/ foetuses examined	1/311	0/344	0/359	1/324
Foetuses with visceral anomalies and or malfunction/foetuses examined	0/101	0/114	0/120	0/108
Foetuses with skeletal malfunction/foetuses examined	0/210	0/230	0/239	0/216
Foetuses with skeletal anomalies/foetuses examined	4/210	4/230	2/239	6/216
Total number malfunction/anomalies	4	4	2	7
% anomalous/malfunction foetuses	1.29	1.16	0.56	2.28

* one female excluded from further calculations due to partial premature birth of part of its litter

** %-values are indicated as per cent of total number of corpora lutea

*** %-values are indicated as per cent of total implantations

Applicant's summary and conclusion

Conclusions:

The substance is not teratogenic in rats at doses of up to 3000 mg/kg bw.