3,5,5-trimethylhexanal

Repeated dose toxicity: oral

Administrative data

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

28 day study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1998

Report date:

1998

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

3,5,5-trimethylhexanal

EC Number:

226-603-0

EC Name:

3,5,5-trimethylhexanal

Cas Number:

5435-64-3

Molecular formula:

C9H18O

IUPAC Name:

3,5,5-trimethylhexanal

Details on test material:

3,5,5-Trimethylhexanal
GLP-Reg.-No. 0637/81 762
Institute-Reg.-No. 0188
Date of production: february/march 1996
Durability: > 1 year
Purity dated 09.05.1996
- 1. 1H und 13C-NMR-spectroscopy: about 97 % Mol-%
- 2. gaschromatography: content: 91,2 mass-%
- 3. water content: 0,05 %
Expiry date: not before may 1998
Properties: clear liquid
Homogeneity: liquid is visually homogeneous
Density (20 ° C): about 0,8184 g/cm3
Solubility in water (20 ° C): < 0,1 g/l
pH: no data
Storage: room temperature, in close containers under inert gas

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Winkelmann GmbH, 33176 Borchen
- Age at study initiation: six to eight weeks
- Weight at study initiation: weight variation did not exceed +/- 20 % of the mean body weight
- Housing: Animals were housed in Makrolon type IV cages, each cage containing 5 rats.
- Diet (e.g. ad libitum): Sniff R 10 diet in pelletform (laboratory standard rat diet), food was offered ad libitum
- Water (e.g. ad libitum): The animals received tap water ad libitum
- Acclimation period: Animals were acclimatized under study conditions (except administraion of test substance) for at least 5 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22° C +/- 3 ° C
- Humidity (%): 30 - 70 %
- Bedding: The bedding used was soft wood Type HW 300/500 W

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:

DIET PREPARATION
- Rate of preparation of diet (frequency): Dosing formulations were prepared weekly. The test substance was transferred to a beaker.
- Mixing appropriate amounts with (Type of food): A corrosponding weight of corn oil, calculated for the target dosages,
was filled into the beaker and war stirred by means of magnetic stirrer for 15 minutes.
- Storage temperature of food: room temperature

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The homogeneity, the concentration and the stability of the test substance formulations were determined by Hüls Infracor GLP-Institute. Samples of all dose levels were taken repeatedly and were analyzed for concentration of the testsubstance.

Duration of treatment / exposure:

28 days (27 days substitute animal No. 19 and 30)

Frequency of treatment:

once a day, seven days per week

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day (nominal)

Remarks:

control

Doses / concentrations 2

Dose / conc.:

50 mg/kg bw/day (nominal)

Remarks:

low dose

Doses / concentrations 3

Dose / conc.:

150 mg/kg bw/day (nominal)

Remarks:

mid dose

Doses / concentrations 4

Dose / conc.:

250 mg/kg bw/day (nominal)

Remarks:

high dose

No. of animals per sex per dose:

3 groups, each of 10 rats (five males and five females) were dosed.

Control animals:

yes, concurrent no treatment

Details on study design:

- Dose selection rationale: The dose levels were chosen based on the results of a range-finding study performed at the Hüls Infracor GLP-Institute
- two female animals of the 500 mg/kg high dose group died. Therefore the highest dose was reduced to 250 mg/kg
- Post-exposure recovery period in satellite groups: 2-week recovery period in the control and high dose groups.

Examinations

Observations and examinations performed and frequency:

An observation of the animals for genearl health state, behavioural changes and toxicosis as well as for mortality was made twice daily, preferably in the early morning and in the late afternoon.
Once a day a clinical observation was performed, preferrable at the same time each dy and considering the peak period of anticipated effects after dosing. At weekends the animals were observed once a day about one hour after application.

Once a week in addition to the normal daily clinical observation a detailed functional observation of each animal was conducted.

In the 4th week of the dosing period an assessment of the motoractivity was performed.

Individual bodyweights were recorded at time of the allocation of animals to groups, prior to dosing on the day of commencement of treatment and subsequently at weekly intervals throughout the study. LAst recordings of bodyweights were performed at the day of necrospy.

Food consumption was measured in weekly intervals throughout the study. Mean food intake was calculated for each rat.

Sacrifice and pathology:

Necrospy
On completion of the dosing period and recovery period animals were killed by CO2-asphyxiation and exsanguniation. A complete autoipsy including a macropathological examination was performed.

Statistics:

Comparisons were performed between vehicle control group and low, medium and high dose groups and between the recovery control group and the high dose recovery group.
Body weights and organ weights were analysed using Kruskal Wallis non parametric analysis of variance.
Haematological data were analysed by ANOVA incorporating a Bartlett's test for homogenicity and variance.

Group means and standard deviation were calculated were appropriate.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

effects observed, treatment-related

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

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

no effects observed

Behaviour (functional findings):

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Effect levels

Dose descriptor:

NOAEL

Effect level:

ca. 250 mg/kg bw/day (nominal)

Sex:

male/female

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

Dose related clinical effects as piloerection and squatting/hunchback position were observed in the male and female high dose groups during the
first functional observation in the "Open filed" after application of the test substance at a dose level of 500 mg/kg/day. Two female animals of the
high dose groups died overnight and were replaced by substitutes. After reduction of the high dose to 250 mg/kg/day on the second day of the
study only individual animals of the high dose groups showed dose-related clinical signs. One female animal of the high dose group died the third day of the study most likely as a result of the application of 500 mg/kg/day the first day of the study. During the recovers period no clinical signs were observed.

High dose femals showed at the end of the treatment period also a statistically significant decrease of absolute bodyweight change (BWCHABS) and a slightly reduced group mean weekly bodyweight (BWN) were compared with control. Evidence of resersibility was found in the recovery groups.

A dose-related decrease of Triglyceride (TRIG) and Total Bilirubin (TBIL) values were observed in animals of both sexes. But apart from the TRIG-
value of the high dose female group all values were within the normal range of our historical backbround data. Evidence of reversibility was found
in the recovery groups.

Centrolobular hypertrophy (minimal slight degree) in correlation with statistically significant higher relative and absolute liver weights and focal
periportal vacuolation in treated females were considered to be substance-related. However, none of the livers examiniated showed nuclear or
cytoplasmic degenerative or necrotic changes of hepatocytes. The female group mean liver weight showed still as statistically significant increase at
the end of the recovery period. But the group mean relative liver weight of treated females showed no statistically significant difference when
compared with female high dose recovery control. It is suggested that the liver changes observed are an expression of a reversible adaptive
response of the liver to the test substnce. As such, it is generally not considered as adverse effect.

The effects caused by the test substance were more pronouned in female animals. None of the effects were irreversible. Therefore, in our
experimental conditions, the no-observed-adverse-effect level (NOAL) is 250 mg/kg/day.

Executive summary:

s. attached background material