(1R,2R,4S)-1,3,3-trimethylbicyclo[2.2.1]heptan-2-ol

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Type of information:

experimental study

Adequacy of study:

key study

Study period:

14 January 1991 - 17 January 1991

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1991

Report date:

1991

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

GLP compliance:

yes (incl. QA statement)

Type of assay:

other: micronucleus assay

Test material

Test material information

Constituent 1

Reference substance name:

Exo-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl acetate

EC Number:

204-727-6

EC Name:

Exo-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl acetate

Cas Number:

125-12-2

Molecular formula:

C12H20O2

IUPAC Name:

(1S,2S,4S) 1,7,7-trimethylbicyclo[2.2.1]hept-2-yl acetate

Test material form:

liquid

Test animals

Species:

mouse

Strain:

NMRI

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: HOECHST AG, Kastengrund, SPF breeding colony
- Age at study initiation: 7 weeks
- Weight at study initiation: 28.7 g (males) and 22.8 g (females)
- Housing: in fully air-conditioned rooms in Macrolon cages (Type 3), on softwood granulate in groups of 5 animals
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 2 °C
- Humidity (%): 55 ± 10 %
- Photoperiod (hrs dark / hrs light): 12 hours light / 12 hours dark

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

- Vehicle(s)/solvent(s) used: sesame oil
- Concentration of test material in vehicle: 20 % (w/v)
- Amount of vehicle (if gavage or dermal): 10 mL/kg bw

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The test sample dilutions were prepared fresh each day. 500 mg test item were weight in a 25 mL flask, mixed with sesame oil and topped up to the calibration mark.

Frequency of treatment:

Once

Post exposure period:

24, 48 and 72 hours (killing times)

Doses / concentrations

Dose / conc.:

2 000 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

70 animals (35 male and 35 female):
Group 1: 0 mg/kg bw (5 males and 5 females) killing time: 24 h post administration
Group 2: 2000 mg/kg bw (5 males and 5 females) killing time: 24 h post administration
Group 4: 0 mg/kg bw (5 males and 5 females) killing time: 48 h post administration
Group 5: 2000 mg/kg bw (5 males and 5 females) killing time: 48 h post administration
Group 6: 0 mg/kg bw (5 males and 5 females) killing time: 72 h post administration
Group 7: 2000 mg/kg bw (5 males and 5 females) killing time: 72 h post administration

Control animals:

yes, concurrent vehicle

Positive control(s):

Endoxan(R). Group 3 (5 males and 5 females) killing time: 24 h post administration
- Route of administration: oral, gavage
- Doses / concentrations: 50 mg/kg bw (0.5% w/v in distilled water , 10 mL/kg bw)

Examinations

Tissues and cell types examined:

Bone marrow erythrocytes cells (from both femora)

Details of tissue and slide preparation:

CRITERIA FOR DOSE SELECTION:
Preliminary studies were conducted to determine the highest administrable non lethal dose level. 3 mice per sex and per dose were exposed to 5000, 4000, 3000 and 2000 mg/kg bw test item.

TREATMENT AND SAMPLING:
After treatment, animals were killed by carbon dioxide asphyxiation 24, 48 and 72 hours after application.

For each animal, about 3 mL foetal bovine serum was poured into a centrifuge tube. Both femora were removed and the bones freed of muscle tissue. The proximal ends of the femora were opened and the bone marrow flushed into the centrifuge tube. A suspension was formed. The mixture was then centrifuged (5 min, 1200 rpm) and almost all the supernatant discarded. One drop of the thoroughly mixed sediment was smeared on a cleaned slide and air-dried for 24 hours. The slides were then stained.

METHOD OF ANALYSIS:
1000 polychromatic erythrocytes were counted for each animal. The number of cells with micronuclei was recorded. As a control measure 1000 mature erythrocytes were also counted and examined for micronuclei. The ratio of polychromatic to normochromatic erythrocytes (PCE/NCE) was determined.

Statistics:

The number of polychromatic erythrocytes with micronuclei and the number of normocytes with micronuclei were evaluated statistically. The comparison of dose groups with the simultaneous control group was performed according to Wilcoxon (paired, one-sided, increase). The results of the treatment groups were compared with the corresponding control values. The ratio of polychromatic to normochromatic erythrocytes was also evaluated statistically by the method of Wilcoxon (paired, two sided). All statistical results were based on a 95% level of significance.

Results and discussion

Test results

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

yes

Remarks:

(see below)

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

RESULTS OF RANGE-FINDING STUDY
- Dose range: 5000, 4000, 3000 and 2000 mg/kg
- Mortality:
At 5000 mg/kg bw: 1/3 males and 2/3 females died;
At 4000 mg/kg bw: 0/3 males and 1/3 females died;
At 3000 mg/kg bw: 0/3 males and 3/3 females died;
At 2000 mg/kg bw: No death were observed.
- Clinical signs of toxicity in test animals: Several clinical signs were observed at 3000-5000 mg/kg bw doses. At 2000 mg/kg bw, uncoordinated gait, increased spontaneous activity and stilted gait was observed.

RESULTS OF DEFINITIVE STUDY
- Mortality: All animals survived.
- Signs of toxicity: uncoordinated gait, increased spontaneous activity. These signs were fully reversible by 5-6 hours after application.
- Induction of micronuclei (for Micronucleus assay): The number of polychromatic (PCE) and normochromatic (NCE) erythrocytes containing micronuclei was not increased.
- Ratio of PCE/NCE (for Micronucleus assay): The ratio of PCE/NCE in both male and female animals remained unaffected by the treatment, and was statistically not different from the control values.
- Positive control: Endoxan induced in both males and females a marked statistically significant increase in the number of polychromatic cells with micronuclei, indicating the sensitivity of the system. the ratio of PCE/NCE was not changed to a significant extent.

Any other information on results incl. tables

Summary of findings in bone marrow erythrocytes:

Sex	Dose (mg/kg)	Sample time	No. animals	Erythrocytes			Erythrocytes with micronuclei
				Poly mean	Normo mean	mean	No	%		Mut I	No	%		Mut I
Male	0	24 h	5	1000	1000	0.92	2	0.16	I	1.0	1	0.08	I	1.0
	2000		5	1000	1000	1.07	2	0.18	-I	1.1	1	0.08	-I	1.0
	Endoxan		5	1000	1000	0.82	23	2.32	*A	14.5	1	0.14	-I	1.7
Female	0		5	1000	1000	1.03	1	0.12	I	1.0	1	0.08	I	1.0
	2000		5	1000	1000	0.86	1	0.08	-I	0.7	0	0.04	-I	0.5
	Endoxan		5	1000	1000	0.79	21	2.10	*A	17.5	2	0.22	*A	2.8
Male	0	48 h	5	1000	1000	0.90	2	0.20	I	1.0	2	0.16	I	1.0
	2000		5	1000	1000	0.78	1	0.08	-I	0.4	0	0.04	-I	0.2
Female	0		5	1000	1000	0.96	1	0.12	I	1.0	1	0.08	I	1.0
	2000		5	1000	1000	0.86	1	0.14	-I	1.2	0	0.04	-I	0.5
Male	0	72 h	5	1000	1000	1.06	2	0.18	I	1.0	0	0.04	I	1.0
	2000		5	1000	1000	1.08	1	0.10	-I	0.6	1	0.10	-I	2.5
Female	0		5	1000	1000	1.05	2	0.20	I	1.0	1	0.08	I	1.0
	2000		5	1000	1000	1.20	1	0.14	-I	0.7	0	0.04	-I	0.5

Mut. I = Mutagenic index

- = No difference from control (P>0.05

I = within the normal range

* = Significantly different from control (P<0.05)

A = Outside the normal range

Applicant's summary and conclusion

Conclusions:

Isobornyl acetate was determined to be not mutagenic in the mammalian erythrocyte micronucleus test.

Executive summary:

An in-vivo micronucleus test was performed with isobornyl acetate according to OECD 474. Five mice per sex and per group (70 in total) were exposed to a single dose of test item at 2000 mg/kg bw, based on preliminary results. Cyclophosphamide was used as a positive control (5 mice per sex). Animals were killed 24, 48 and 72 hours after administration of the test compound. For each animal, bone marrow smears were flushed from both femora and the slides were prepared for erythrocyte micronuclei observation. The number of polychromatic and normochromatic erythrocytes containing micronuclei was not increased. The ratio of polychromatic/normochromatic erythrocytes in both male and female animals remained unaffected by the treatment and was statistically not different from the control values, indicating no mutagenicity. Based on these results, isobornyl acetate was determined to be not mutagenic in the mammalian erythrocyte micronucleus test.