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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1997-03-24 - 1997-04-9
Reliability:
2 (reliable with restrictions)
Justification for type of information:
please see category approach

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1998
Report date:
1998

Materials and methods

Test guideline
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
GLP compliance:
yes (incl. QA statement)
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
2-butyloctanoic acid
EC Number:
248-570-1
EC Name:
2-butyloctanoic acid
Cas Number:
27610-92-0
Molecular formula:
C12H24O2
IUPAC Name:
2-butyloctanoic acid
Test material form:
liquid
Details on test material:
- Name of test material: 2-butyl octanoic acid
- Molecular formula: C12H24O2
- Molecular weight: 200.32 g/mole
- Smiles notation: O=C(O)C(CCCCCC)CCCC

Test animals

Species:
rat
Strain:
CD-1
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source:Charles River (UK) Limited, Margate, Kent, England on 21 March 1997
- Age at study initiation: ca 9 weeks of age on arrival
- Weight at study initiation: 196-274 g
- Fasting period before study: not mentioned
- Housing: The females were housed singly in polypropylene cages with stainless steel grid bottoms and mesh tops, measuring 42 x 27 x 20 cm. A separate stainless steel food hopper and a polycarbonate water bottle were provided for each cage. Excreta were collected on a tray, lined with absorbent paper, suspended beneath each cage. The cages were suspended on racks, each full rack containing 6 rows of 4 cages.
Cages, tray paper and water bottles were changed as required.
- Diet (e.g. ad libitum): Rat and Mouse Breeder Diet No. 3 (Expanded) SQC, the diet was supplied with a batch analysis for nutritive constituents and a range of significant contaminants.
- Water (e.g. ad libitum): domestic mains water
- Acclimation period: for 3-5 days prior to commencement of treatment.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 ± 2
- Humidity (%): 50 ± 15
- Air changes (per hr): 15-20
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 1997-02-21 To: 1997-04-09

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
other: sodium hydroxide solution in water, adjusted at pH 9.5
Details on exposure:
The test material was administered orally (by gavage) because this is a likely route of exposure in man. Dosing was performed once daily at approximately the same time each day. The highest concentration of dose formulation was prepared by mixing equimolar amounts of test material and sodium hydroxide (diluted in water for irrigation). Lower dose concentrations were then prepared by serial dilutions in water for irrigation and adjusted to approximately pH 9.5 with sodium hydroxide. All solutions were mixed by manual inversion until visibly homogenous. The Control animals received water for irrigation.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The analysed concentrations of the dose formulations were within 4 % of the nominal indicating accurate formulation of the test material, the low coefficients of variation indicated that the formulation were homogenous. In the proposed method, samples of gavage dosing solutions are spiked with Lauric Acid as internal standard, diluted with mobile phase as necessary and analysed by HPLC with UV detection at 212 nm.
The limit of quantification was investigated and shown to be ca. 11 µg/ml. The chromatographic system has been shown to be linear over a range of ca. 0-165 µg/ml for the test substance in solution. The coefficient of correlation obtained was 0.9996. The overall accuracy was 101% and the assay precision, expressed as a coefficient of variation (n=10) was 2.9 %. Determination of the system precision showed a coefficient of variation of 0.7 % for samples equivalent to ca. 99 µg/ml. The stability test indicated that the test substance is stable at least 11 days in mobile phase when stored at ambient laboratory temperature in the dark. Gavage solutions containing ca 1 mg/ml and ca 100 mg/ml test substance were shown to be accurately and homogenously formulated. Gavage solutions were shown to be stable for at least 1 day, when stored at ambient laboratory temperature in the dark at least 7 days, when stored at 2-8 °C.
Details on mating procedure:
No more than 2 females were inseminated by the same male, and the identity of each male was provided.
Duration of treatment / exposure:
The animals were dosed once daily at approximately the same time each day over days 6-19 (inclusive) of gestation.
Frequency of treatment:
once daily at a volume of 10 ml dosing formulation per kg of body weight, using a steel dosing cannula.
Duration of test:
altogether 16 days, 14 days of exposure
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
25 mg/kg bw/d
Basis:
other: gavage
Remarks:
Doses / Concentrations:
200 mg/kg bw/d
Basis:
other: gavage
Remarks:
Doses / Concentrations:
400 mg/kg bw/d
Basis:
other: gavage
No. of animals per sex per dose:
25
Control animals:
other: water
Details on study design:
- Dose selection rationale: A preliminary study was conducted with 125; 250; 500; 1000 mg/kg bw/d. Mated female Sprague-Dawley rats were dosed orally by gavage over days 6-19 inclusive of gestation. They were killed on day 20 of gestation for evaluation of pregnancy outcome. Body weight loss and a marked decrease in food consumption were observed at 1000 mg/kg bw/d. One animal had a premature death, the study was terminated for the highest dose group. There were treatment related clinical observations in all groups, the type and severity of the finding was dependent upon the dose: Staggering, altered respiration, dark and/or partially closed eyes, skin cold to touch, subdued behaviour, hunched appearance, piloerection and transient salivation. At 500 mg/kg bw/d principal findings were the clinical observations. Slightly reductions in group mean foetal weights were observed, but there was no evidence of any effects on foetal survival. At 250 and 100 mg/kg bw/d any changes observed in body weight gain and food consumption were considered too small to be attributed to treatment. There was no effect of treatment on pregnancy perfomace or foetal weight. In conclusion, the findings at 1000 and 500 mg/kg bw/d precluded the use of either of these dose levels in a subsequent developmental toxicity study. However, maternal toxicity at 250 mg/kg bw/d was manifest principically as clinical observations and there was concern that there my be few effects seen at this level. Based on that study for the main study the levels were 0; 25; 200 and 400 mg/kg bw/d (study report Inveresk, 491708).


Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: No

DETAILED CLINICAL OBSERVATIONS: Yes, all animals: examined to treatment, the nature, onset, duration and intensity of any signs were recorded, a specific examination being made 1-2 h after dosing.
- Time schedule: at the beginning and and the end of each day

BODY WEIGHT: Yes
- Time schedule for examinations: days 4 and 6-20 of gestation

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes, the weight of the food consumed by each animal was recorded daily, commencing on day 4 of gestation (weighed quantity first offered on day 3, residue recorded on day 4).

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 20, the females were killed by carbon dioxide asphyxiation, foetuses were killed by chilling at ca. 4 °C for approximately 10 min.
Ovaries and uterine content:
No data
Fetal examinations:
fetal weight, fetal abonormalities, variants, skeletal ossification paramaters
Statistics:
mean body weight gains over days 6 to 9, 9 to 13, 13 to 20, 6 to 20 were analysed. Analysation by the Kruskal-Wallis test. Mean foetal weights were analyses by the Kruskal-Wallis test. For the other reproductive parameters no statistical evaluation was done.
Historical control data:
Not mentioned

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
clinical observations in all animals, including altered respiration pattern, piloerection, hunched appearance, red/brown staining of coat, and salivation. It was necessary to discontinue dosing for 4 animals, and 2 of these were subsequently killed because of their condition.
Dermal irritation (if dermal study):
not examined
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
There were decreases in body weight gain and food consumption during the middle part of the dosing period. There were no obvious effects on body weight or food consumption at the lower levels.
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
no effects observed
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
no effects observed
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
no effects observed
Immunological findings:
no effects observed
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Neuropathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Other effects:
no effects observed

Maternal developmental toxicity

Number of abortions:
no effects observed
Pre- and post-implantation loss:
no effects observed
Total litter losses by resorption:
no effects observed
Early or late resorptions:
no effects observed
Dead fetuses:
no effects observed
Changes in pregnancy duration:
no effects observed
Description (incidence and severity):
Migrated Data from removed field(s)
Field "Effects on pregnancy duration" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsMaternalAnimals.MaternalDevelopmentalToxicity.EffectsOnPregnancyDuration): no effects observed
Changes in number of pregnant:
no effects observed
Other effects:
no effects observed
Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
At 400 mg/kg bw/d there were decreases in body weight gain and food consumption during the middle part of the dosing period. There were no obvious effects on body weight or food consumption at the lower levels.
Maternal toxicity at 400 mg/kg bw/d was manifest as clinical observations in all animals, including altered respiration pattern, piloerection, hunched appearance, red/brown staining of coat, and salivation. It was necessary to discontinue dosing for 4 animals, and 2 of these were subsequently killed because of their condition.
At 200 mg/kg bw/d maternal toxicity was limited to clinical observations including altered respiration pattern, hunched appearance and piloerection.
There was no indication of maternal toxicity at 25 mg/kg bw/d.

Effect levels (maternal animals)

open allclose all
Key result
Dose descriptor:
LOAEL
Effect level:
200 mg/kg bw/day (nominal)
Based on:
test mat.
Basis for effect level:
other: maternal toxicity
Key result
Dose descriptor:
NOAEL
Effect level:
25 mg/kg bw/day (nominal)
Based on:
test mat.
Basis for effect level:
other: maternal toxicity

Results (fetuses)

Fetal body weight changes:
effects observed, treatment-related
Description (incidence and severity):
At 400 mg/kg bw/d there was a significant decrease in mean foetal weight. At 25 and 200 mg/kg bw/d mean foetal weights were not signicantly different from Control.
Migrated Data from removed field(s)
Field "Fetal/pup body weight changes" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsFetuses.FetalPupBodyWeightChanges): effects observed, treatment-related
Field "Description (incidence and severity)" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsFetuses.DescriptionIncidenceAndSeverityFetalPupBodyWeightChanges): At 400 mg/kg bw/d there was a significant decrease in mean foetal weight. At 25 and 200 mg/kg bw/d mean foetal weights were not signicantly different from Control.
Reduction in number of live offspring:
no effects observed
Changes in sex ratio:
no effects observed
Changes in litter size and weights:
no effects observed
Changes in postnatal survival:
no effects observed
External malformations:
no effects observed
Skeletal malformations:
effects observed, treatment-related
Description (incidence and severity):
Among the minor foetal abnormalities, the incidence of supernumerary (14th) ribs at 400 mg/kg bw/d was greater than Control. The incidences of supernumerary ribs at 25 and 200 mg/kg bw/d were slightly greater than Control, but these incidences were within the recent background range and were not obviously associated with treatment. The incidences of the other minor foetal abnormalities did not indicate any effect of treatment. At 400 mg/kg bw/d there was a slight increase in the number of foetuses with unossified 5th metacarpals and the number of sternebrae incompletely ossified. These findings were considered to reflect the decrease in foetal weight noted at this dose level. The slight changes in the foetal ossification parameters at the lower levels were considered too small to be associated with treatment.
Visceral malformations:
not specified
Other effects:
no effects observed
Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:yes. Remark: only minor effects at the hightes dose group, only in maternal toxic dosages

Details on embryotoxic / teratogenic effects:
At 400 mg/kg bw/d there was a significant decrease in mean foetal weight. At 25 and 200 mg/kg bw/d mean foetal weights were not signicantly different from Control. Among the minor foetal abnormalities, the incidence of supernumerary (14th) ribs at 400 mg/kg bw/d was greater than Control. The incidences of supernumerary ribs at 25 and 200 mg/kg bw/d were slightly greater than Control, but these incidences were within the recent background range and were not obviously associated with treatment. The incidences of the other minor foetal abnormalities did not indicate any effect of treatment. At 400 mg/kg bw/d there was a slight increase in the number of foetuses with unossified 5th metacarpals and the number of sternebrae incompletely ossified. These findings were considered to reflect the decrease in foetal weight noted at this dose level. The slight changes in the foetal ossification parameters at the lower levels were considered too small to be associated with treatment.

Effect levels (fetuses)

open allclose all
Key result
Dose descriptor:
LOAEL
Effect level:
400 mg/kg bw/day (nominal)
Based on:
test mat.
Basis for effect level:
other: fetotoxicity
Key result
Dose descriptor:
NOAEL
Effect level:
200 mg/kg bw/day (nominal)
Based on:
test mat.
Basis for effect level:
other: fetotoxicity

Fetal abnormalities

Key result
Abnormalities:
not specified

Overall developmental toxicity

Key result
Developmental effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
In conclusion, under the conditions of this study, the maternal No Effect Level was considered to be 25 mg/kg bw/d and the foetal No Effect Level was considered to be 200 mg/kg bw/d.
Executive summary:

2-butyl octanoic acid was investigated for developmental toxicity testing in rats. Mated female Sprague-Dawley rats were randomised into 4 treatment groups, each containing 25 animals. These animals were dosed orally by gavage once daily over Days 6-19 inclusive of gestation, where Day 0 was the day of detection of mating. The dose levels applied were 0 (control); 25; 200 and 400 mg/kg bw/d.

The animals were monitored during gestation for clinical signs of toxicity and for body weight, food and water consumption performance. They were killed on Day 20 of gestation for evaluation of pregnancy outcome. The live foetuses were subsequently examined for abnormalities and variants of the viscera and skeleton. Maternal toxicity at 400 mg/kg bw/d 2 -butyloctanoic acid was manifest as clinical observations in all animals, including altered respiration pattern, piloerection, hunched appearance, red/brown staining of coat, and salivation. It was necessary to discontinue dosing for 4 animals, and 2 of these were subsequently killed because of their condition. At 200 mg/kg bw/d maternal toxicity was limited to clinical observations including altered respiration pattern, hunched appearance and piloerection. There was no indication of maternal toxicity at 25 mg/kg bw/d. At 400 mg/kg bw/d there were decreases in body weight gain and food consumption during the middle part of the dosing period. There were no obvious effects on body weight or food consumption at the lower levels. At 400 mg/kg bw/d mean foetal weight was lower than control, and there was an increased incidence of supernumerary ribs. Foetal ossification at 400 mg/kg bw/d was slightly reduced, as indicated by an increased incidence of incomplete ossification affecting the sternebrae and digital bones, probably associated with the decrease in foetal weight. There were no obvious foetal effects at 25 or 200 mg/kg bw/d. There was no obvious effects of treatment on pregnancy performance (including the incidence and survival of implants) at any of the dose levels applied.

In conclusion, under the conditions of this study, the maternal No Effect Level was considered to be 25 mg/kg bw/d and the foetal No Effect Level was considered to be 200 mg/kg bw/d. In not maternal toxic dosages no teratogenic effects were found. Therefore the substance is considered to be not developmental toxic.