7-methyl-3-methyleneocta-1,6-diene

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1993

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

Study well documented and conducted similarly to OECD Guideline 414 with deviations: mating conditions (1 male for 3 females); food consumption not followed; bodyweight only recorded at Day 0, 6, 16 and 20 of gestation

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1993

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

yes

Remarks:

mating conditions (1 male for 3 females); food consumption not followed; bodyweight only recorded at Day 0, 6, 16 and 20 of gestation

Principles of method if other than guideline:

Not applicable

GLP compliance:

not specified

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

7-methyl-3-methyleneocta-1,6-diene

EC Number:

204-622-5

EC Name:

7-methyl-3-methyleneocta-1,6-diene

Cas Number:

123-35-3

Molecular formula:

C10H16

IUPAC Name:

7-methyl-3-methylideneocta-1,6-diene

Test material form:

liquid

Test animals

Species:

rat

Strain:

Wistar

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Oswaldo Cruz Foundation Central Animal House breeding stock
- Housing: Housed in plastic cages with wood shavings as bedding
- Diet (e.g. ad libitum): Nuvital diet for laboratory animals, Nuvilab Ltd, Curitiba, Brazil; ad libitum
- Water (e.g. ad libitum): Tap water; ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21-23 °C
- Photoperiod (hours dark / hours light): 12 hours dark / 12 hours light

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: Test material was dissolved in corn oil

Analytical verification of doses or concentrations:

not specified

Details on analytical verification of doses or concentrations:

Not applicable

Details on mating procedure:

- Impregnation procedure: Cohoused
- If cohoused:
- M/F ratio per cage: 1:3
- Length of cohabitation: 2 h
- Proof of mating: Sperm in vaginal smear referred to as Day 0 of pregnancy

Duration of treatment / exposure:

10 days (Day 6-15 of pregnancy)

Frequency of treatment:

Once daily

Duration of test:

20 days

No. of animals per sex per dose:

Treated females: 22-36; pregnant females: 16-29

Control animals:

yes, concurrent no treatment

yes, concurrent vehicle

Details on study design:

Control animals: as no statistically significant difference was found between the untreated and the vehicle treated control animals, in any of the parameters analysed, the data of both groups were pooled and were thereafter designated the control group.

Examinations

Maternal examinations:

BODY WEIGHT: Yes
- Time schedule for examinations: Days 0, 6, 16 and 20 of pregnancy

Ovaries and uterine content:

The uterine content was examined after termination: Yes, animals were sacrificed on Day 20 for caesarean examinations
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of living and dead foetuses: Yes
- Number of implantations: Yes
- Number of resorptions: Yes

Fetal examinations:

- External examinations: Yes [all living foetuses]; weighed and examined for externally visible malformations
- Soft tissue examinations: Yes [5-7 litters per group]: evaluated for visceral malformations; heart, lungs, thymus, liver, spleen and kidneys were weighed and microdissected
- Skeletal examinations: Yes [all the remaining litters]

Statistics:

- Statistical analysis was by one way analysis of variance or, alternatively, by the Kruskal-Wallis test whenever the data did not fit a normal distribution
- Statistically significant differences between groups were tested by using a two sided Student's t-test or the Mann-Whitney U-test
- Proportions were analysed by the chi-square test
- Difference was considered to be statistically significant at P < 0.05

Indices:

No data

Historical control data:

No

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Mortality:

mortality observed, treatment-related

Description (incidence):

At 1200 mg/kg bw/d: 1/29 dams died on Day 11 of pregnancy

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Statistically significant decrease in weight gain during days 6-11 of pregnancy (17.3 ± 7 g vs. 3.2 ± 13.2 g in control vs. 1200 mg/kg group, respectively)

Maternal developmental toxicity

Pre- and post-implantation loss:

effects observed, treatment-related

Description (incidence and severity):

Number of visible implantation sites was significantly reduced (12.6 ± 2.2 vs. 10.2 ± 2.9 in control vs. 1200 mg/kg group, respectively)

Effect levels (maternal animals)

Dose descriptor:

NOAEL

Effect level:

500 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

body weight and weight gain

mortality

Results (fetuses)

Fetal body weight changes:

effects observed, non-treatment-related

Description (incidence and severity):

Treatment-related effects on foetal weight were only very slight, or even insignificant, if the litter is taken as the statistical unit of analysis

External malformations:

effects observed, treatment-related

Description (incidence and severity):

Increased frequency of irregularly positioned hind paws was observed in 1200 mg/kg bw/day group

Visceral malformations:

effects observed, treatment-related

Description (incidence and severity):

Visceral malformations such as enlarged ureters associated with an enlarged renal pelvis (one control foetus and one in 1200 mg/kg group), shorter ureter (one control foetus and one in 250 mg/kg bw/day group) and accessory (seventh) lobe in the liver (three foetus in 250 mg/kg bw/day group)

Other effects:

effects observed, treatment-related

Description (incidence and severity):

Increased incidence of delayed ossification and minor gross structural anomalies in the foetal skeleton were observed in 1200 mg/kg bw/day group

Effect levels (fetuses)

Key result

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: higher incidence of signs of retardation and of anomalies in the foetal skeleton observed at 1200 mg/kg bw/day

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Table 1. Occurrence of delayed ossification in foetuses of rats treated orally with β-myrcene on Days 6-15 of pregnancy

	β-Myrcene (mg/kg bw)
Treatment	0	250	500	1200
Foetuses examined (no.)	114	106	116	209
Percentage of foetuses with signs of delayed ossification^αin:
Skull bones	4.4	0.9	3.4	9.6*
Caudal vertebrae	7	2.8	6	37.8*
Forelimbs/metacarpus	2.6	0	0.9	9.1*
Hind limbs/metatarsus	5.3	2.8	3.4	29.2*

^α Signs of delayed ossification: not ossified (whole bone is not stained), poorly ossified (whole bone is poorly stained), and irregular spongy bones.

* P < 0.05; chi-square test

Applicant's summary and conclusion

Conclusions:

The no-observed-adverse-effect level (NOAEL) for maternal toxicity and for embryo-foetotoxicity of β-myrcene administered orally (gavage) was considered to be 500 mg/kg bw/day in Wistar rats.

Executive summary:

A study comparable to Guideline OECD 414 was conducted to evaluate the embryo-foetotoxic potential of β-myrcene in the Wistar rats.

β -Myrcene (at 250, 500 and 1200 mg/kg bw/day) in corn oil was given orally to Wistar rats from Day 6 to 15 of pregnancy. Two control groups, one received vehicle only and another without treatment, were also studied simultaneously. All rats were weighed on Day 0, 6, 16 and 20 of pregnancy. Caesarean sections were performed on Day 20 of pregnancy, and the number of resorptions and implantation sites were recorded. Foetuses were weighed and examined for external, visceral and skeletal malformations.

No adverse effects on the offspring were seen with the lowest dose tested, but at 500 mg/kg bw/day and higher doses, decreased birth weight, increased perinatal mortality and delayed day of appearance of landmarks of postnatal development were observed. Moreover, fertility was impaired in female offspring exposed to the two highest doses of β-myrcene. However it is difficult to know if this effect was related to reprotoxicity or due to the general toxicity observed at these dose-levels.

Therefore, the no-observed-adverse-effect level (NOAEL) for maternal toxicity and for embryo-foetotoxicity of β -myrcene administered orally (gavage) was considered to be 500 mg/kg bw/day in Wistar rats.