Carboxylic acids, C5-9

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Hypothesis for the analogue approach: This read-across is based on the hypothesis that source and target substances have similar toxicological properties because, following oral intake, the source substances hydrolyse in the gut to non-common products predicted to have no toxicological effect (metabolic approach). The target substance is n-nonanoic acid, a saturated linear, medium-chain length carboxylic acid. The prediction is limited for saturated linear, medium-chain length carboxylic acids as source substances and for systemic toxicity endpoints, e.g. repeated dose toxicity and toxicity to reproduction. The prediction is supported by valid toxicological data on the substances and their hydrolysis products, based on known rapid and extensive hydrolysis and subsequent metabolism. For read across justification, see the atteched file in endpoint 13 ( Analogue approach justification): Acceptable, well-documented publication which meets basic scientific principles

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1997

Report date:

1997

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

yes

Remarks:

2 doses tested

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

medium chain triglycerides

IUPAC Name:

medium chain triglycerides

Details on test material:

- Name of test material (as cited in study report): Medium Chain Triglycerides (MCT)
- Test article: a 20% lipid emulsion containing a 3:1ratio of MCT:LCT from soy bean oil
- Molecular weight: the 20% lipid emulsion is composed primarily of 8- and 10-carbon fatty acids and a trace of 6- and 12-carbon fatty acids.
- Substance type: triglycerides
- Physical state: emulsion
- Stability of test material: analytically determined to be stable

Test animals

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: HRP Inc, Denver, PA, USA
- Age at study initiation: 5.5 to 6.5 months
- Weight at study initiation: 330 to 4446 g on GD 0
- Housing: singly
- Diet: ad libitum except during dose administration
- Water: ad libitum except during dose administration
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
air-conditioned rooms

Administration / exposure

Route of administration:

other: intravenous infusion (ear vein)

Vehicle:

soya oil

Details on exposure:

VEHICLE
- Justification for use and choice of vehicle (if other than water): for reasons of solubility
- Concentration in vehicle: 3.1 ratio of MCT:LCT from soya oil

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Stability was analytically determined which implies analytical verification of composition and doses. Methods were not described.

Details on mating procedure:

Time-mated animals; no further details described.

Duration of treatment / exposure:

GD 7 through 19

Frequency of treatment:

daily, 5h/day

Duration of test:

until GD 29

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 1, and 4.28 g/kg bw and day
Basis:
other: i.v. dose

No. of animals per sex per dose:

15

Control animals:

yes, sham-exposed

Details on study design:

- Dose selection rationale: 4.28% was the highest dose in preclinical studies that did not produce narcosis

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: at least daily

BODY WEIGHT: Yes
- Time schedule for examinations: pre-dose and on GD5 through GD20

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): n. a.

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): n.a.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 29

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes

Fetal examinations:

- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: half per litter
- Skeletal examinations: Yes: half per litter
- Head examinations: Yes

Statistics:

The litter was the experimental unit for evaluation and all comparisons were made with the control group. Amongst other calculations, ANOVA followed by Dunnett's test was used to analyse body weights, feed consumption, caesarian section data. Foetal abnormality data were analysed using the Cochran.-Armitage test and the Fisher-Irwin exact test.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
All low-dose animals survived whereas one control and one high-dose rabbit were sacrificed after aborting on GD 20; the treated animal had the lowest feed consumption in the group. The abortion was inside the historical control range and there were no remarkable necropsy findings for either animal.
The only clinical sign noted was that 3/15 animals had no fecal output for 1 day during the treatment period. Body weights were comparable, but feed consumption and body weight gain were significantly reduced (p<0.01) during the treatment period (GD 12 through GD20) and also in the recovery period thereafter (until GD 29). Reduced feed consumption was expected due to the high caloric nature of the test material.

Effect levels (maternal animals)

1

Dose descriptor:

NOAEL

Effect level:

ca. 1 000 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

2

Dose descriptor:

NOAEL

Effect level:

ca. 1 000 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: developmental toxicity

3

Dose descriptor:

NOAEL

Effect level:

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

Based on:

other: nonanoic acid

Basis for effect level:

other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
At the low dose (1000 mg/kg bw and day) foetal postimplantation was slightly increased and the mean body weight was slightly reduced without gaining a level of significance This was, however, the case at the high dose where early and late resorptions were clearly increased; as a consequence, the number of live foetuses was decreased (p<0.01), and the mean foetal weight was significantly decreased (p<0.01); cf. table 3. The incidence of external, soft tissue and skeletal malformations was increased at the high dose (statistically significant); tables 3 and 4.
The incidence of soft tissue findings was also increased in low dose foetuses, but without gaining a level of significance (tables 3 and 4) when individual malformations were analysed statistically. Similarly, skeletal findings were increased in the low dose group without gaining a level of significance (table 4).

Effect levels (fetuses)

1

Dose descriptor:

NOAEL

Effect level:

ca. 1 000 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: teratogenicity

2

Dose descriptor:

NOAEL

Effect level:

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

Based on:

other: nonanoic acid

Basis for effect level:

other: teratogenicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

 

 

 

Applicant's summary and conclusion

Conclusions:

Intravenous doses of MCT (up to 4280 mg/kg bw and day, GD 5-20) caused maternal effects at the high dose, but no developmental toxicity or teratogenicity. The NOAEL was therefore 1000 mg/kg bw and day for maternal toxicity and 4280 mg/kg bw and day for developmental toxicity and teratogenicity.

Executive summary:

Time-mated rabbits (15/group) received intravenous infusions into the ear vein (duration 5 h/day) during Gestation Days 7 through 19 of a 20% lipid emulsion that contained a ratio of 3:1 of MCT and Long Chain Triglycerides (LCT) from soy bean oil at doses of 1 and 4.28 g/kg bw and day. Controls received 0.9% saline. Medium chain fatty acids are 6 to 12 carbons in length. The 20% lipid emulsion is composed primarily of 8- and 10-carbon fatty acids, with only traces of 6- and 12-carbon fatty acids. The does were observed for clinical signs and sacrificed at termination, the does and of the uterus content were examined.

No treatment-related mortalities were noted. The only clinical sign was a reduced faecal output of 3/15 does on one day. Body weight change and feed intake was significantly reduced (p<0.01) in high-dose rabbits which was expected because of the high caloric test material. No adverse effect was noted in does at 1000 mg/kg bw and day, hence this was considered to represent the maternal NOAEL value.

 

Foetal findings: at the low dose (1000 mg/kg bw and day) foetal postimplantation loss was slightly increased and the mean foetal weight was slightly reduced without gaining a level of significance. This was, however, the case at the high dose where early and late resorptions were clearly increased; consequently, the number of live foetuses was decreased (p<0.01), and the mean foetal weight was significantly decreased (p<0.01). The incidence of external (p<0.05), soft tissue and skeletal malformations (p<0.05) was increased at the high dose.

The incidence of soft tissue findings was also increased in low dose foetuses, but without gaining a level of significance when individual malformations were analysed statistically. Similarly, an increase of skeletal findings was seen in the low dose group below a level of significance. Based on these findings the NOAEL for developmental toxicity was set at 1000 mg/kg bw and day, and the authors assume that the findings at 4280 mg/kg bw and day are attributable to the low feed consumption and malnutrition rather than a direct teratogenic effect of the test material (Henwood et al. 1997).

The study is considered to be valid. The intravenous route was used because the parenteral route is used in patients that cannot meet their nutritional needs by the conventional oral route, and 1000 mg/kg bw and day is the approximate clinical dose, whereas 4280 mg/kg bw and day is reportedly the highest preclinical dose that did not cause narcosis.

The study can be used for the assessment of n-nonanoic acid in a way as this has been described in the repeated dose toxicity section for the studies of Matulka and Webb who also administered triglycerides as test material. In brief,

-         the metabolism of straight chain fatty acids of 8 to 10 carbons including nonanoic acid is very similar and includes rapid degradation via ß-oxidation, which justifies cross reading form C8 and C10 fatty acids to C9 nonanoic acid.

-         The fatty acid composition of the test material of this study (Henwood et al., 1997) was almost exclusively C8 and C10, with traces of C6 and C12.

-         The mean molecular weight of the triglycerides is calculated assuming that traces are negligible, and that C8 and C10 are present in equimolar proportions (this was not specified in the publication). Then, the mean triglyceride molecular weight is 596, and the two fatty acids represent 42.5% each of the molecular weight, and also of the dose, i.e. approx. 425 mg of C8 and also of C10 fatty acid/kg bw and dose.

In a weight of evidence approach, this result can be used to assess n-nonanoic acid: NOAEL approx. 425 mg/kg bw and day.