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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:
11 Sept. 1978 - 6 Oct. 1978
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Comparable to guideline study.
Justification for type of information:
A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
Cross-reference
Reason / purpose for cross-reference:
read-across: supporting information
Reference
Endpoint:
developmental toxicity
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
11 Sept. 1978 - 6 Oct. 1978
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Comparable to guideline study.
Justification for type of information:
A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
Reason / purpose for cross-reference:
read-across source
Details on maternal toxic effects:
Maternal toxic effects:no effects

Details on maternal toxic effects:
There was no mortality in either of the dosage groups. Pregnancy rates were comparable between the exposure groups and negative controls. Weight gain was significantly higher in the exposure groups post-dosing. There were no significant clinical observations in either exposure group. The mean number of corpora lutea was significantly decreased in the 300 ppm group. Since ovulation occurred prior to exposure, this was not considered to be treatment related. The mean number of implantations was comparable between exposure groups and negative controls. The implantation efficiency values were actually significantly higher in exposure groups as compared to negative controls. The mean number of live fetuses, resorption sites, and number of dams with more than one resorption site were comparable between exposures and negative controls. The gross postmortem examination of dams showed no treatment related effects.
Key result
Dose descriptor:
NOAEC
Effect level:
>= 300 ppm
Basis for effect level:
other: Systemic toxicity
Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
The body weights of fetal males in the 100 ppm group were significantly higher than negative controls. There were some statistically significant differences in mean crown-rump distance between both dosage levels and negative controls, these differences were slight and the effect inconsistant between dosages and sex. These differences were therefore not considered to be indicative of a treatment related effect. Mean numbers of male and female fetuses, and sex ratios were similar between exposure groups and negative controls. Ossification variations were similar in exposure groups and negative controls, as was the incidence of litters with fetuses containing ossification variations. No malformations externally or in the soft tissues were noted in the fetuses except in the positive controls. Though skeletal defects were noted in the exposure group, the types of malformations are common in rat fetus and not considered to be treatment related.
Key result
Dose descriptor:
NOAEC
Effect level:
>= 300 ppm
Based on:
test mat.
Basis for effect level:
other: Developmental Toxicity
Abnormalities:
not specified
Developmental effects observed:
not specified

Results - Dams

Endpoint

Negative Control

400 mg/kg ASA

100 ppm

300 ppm

Pregnancy Rate (%)

100.0

95.0

100.0

90.0

Mortality Rate (%)

0.0

10.0

0.0

0.0

Mean Body Weight Gain  (g)

Dams - Days 15-21

84

32

108

103

Mean Corpora Lutea

15.2

14.5

15.5

13.8

Mean No. Implantations

13.0

13.2

13.8

13.2

Implantation Efficiency (%)

85.8

91.1

88.7

95.6

Mean No. Live Fetuses

12.5

7.4

12.9

12.6

Mean No. Dead Fetuses

0.0

0.0

0.0

0.0

Mean No. Resorptions

0.6

5.8

0.9

0.7

Dams with more than one Resorption (%)

10.0

58.8

25.0

11.1

Results – Fetuses

Endpoint

Negative Control

400 mg/kg ASA

100 ppm

300 ppm

Male Mean Fetal Weight (g)

5.57

3.88

5.82

5.62

Female Mean Fetal Weight (g)

5.29

3.62

5.44

5.33

Male Mean Crown-Rump Distance (cm)

4.3

3.7

4.4

4.2

Female Mean Crown-Rump Distance (cm)

4.2

3.6

4.2

4.1

Sex Ratio (%)

91.5

98.4

88.3

105.5

Ossification Variations (%)

70.7

100.0

79.4

79.3

Litters with Ossification Variations (%)

100.0

100.0

95.0

100.0

Soft Tissue Malformations (%)

2.4

26.8

1.1

3.9

Litters with Soft Tissue Malformations (%)

10.0

54.5

5.0

16.7

Gross Evisceration Malformations (%)

5.4

3.6

1.8

4.0

Litters with Gross Evisceration Malformations

25.0

8.3

10.0

16.7

Skeletal Malformations (%)

0.0

21.4

2.9

1.3

Litters with Skeletal Malformations

0.0

66.7

15.0

11.1

Conclusions:
The NOAEC for developmental toxicity in rats is >=300 ppm (1575 mg/m3) via inhalation. The test substance is also non-teratogenic.
Executive summary:

This data is being read across from the source study that tested Hydrocarbons, C9-C12, n-alkanes, isoalkanes, cyclics, aromatics (2-25%) based on analogue read across.

This study determined the developmental toxicity of MRD-78 -25 in rats exposed via inhalation. Groups of 20 pregnant female rats were exposed 6 hrs/day during days 6 -15 of gestation. Test concentrations of 100 or 300 ppm test substance. In addition to a negative control group, there was also a positive control group that was exposed to acetylsalicylic acid on days 6 -15 of gestation. Dams were observed for toxicological signs and pharmacological effects. On day 21 of gestation, the animals were sacrificed, and examined for corpora lutea and uterine implantation parameters. Fetuses were examined for fetal size, sex ratio, and external, soft-tissue, and skeletal malformations. No adverse effects due to exposure to the test substance were seen in either dams or fetuses. No treatment related malformation effects were noted in the fetuses. The developmental NOAEC for rats by inhalation is >=300 ppm. The test substance is also not teratogenic.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1979
Report date:
1979

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
other: Guidelines for Reproduction Studies for Safety and Evaluation of Drugs for Human Use, Segment II (Teratology Study)
GLP compliance:
no
Limit test:
yes

Test material

Constituent 1
Chemical structure
Reference substance name:
Hydrocarbons, C9-C12, n-alkanes, isoalkanes, cyclics, aromatics (2-25%)
EC Number:
919-446-0
Molecular formula:
None available. Not a single isomer, see remarks.
IUPAC Name:
Hydrocarbons, C9-C12, n-alkanes, isoalkanes, cyclics, aromatics (2-25%)

Test animals

Species:
rat
Strain:
Sprague-Dawley
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc.
- Age at study initiation: 7 weeks
- Fasting period before study: Animals were not given food during exposure.
- Housing: Individually, except during mating, in stainless steel cages, animals identified by ear tags
- Diet (e.g. ad libitum): Purina Lab Chow, ad libitum
- Water (e.g. ad libitum): Elizabethtown Water Company, ad libitum
- Acclimation period: Aug. 17, 1978-Sept. 4, 1978


ENVIRONMENTAL CONDITIONS
- Temperature (°C): monitored twice daily, room temperature
- Humidity (%): dry air
- Photoperiod (hrs dark / hrs light): 12 hrs light/12 hrs dark


IN-LIFE DATES: days 6-15 of gestation From: 11-27 Sept. 1978 To: 20 Sept. - 6 Oct. 1978

Administration / exposure

Route of administration:
inhalation: vapour
Vehicle:
unchanged (no vehicle)
Details on exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: one cubic meter exposure chamber
- Temperature, humidity, pressure in air chamber: room temperature, dry air
Analytical verification of doses or concentrations:
no
Details on mating procedure:
- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1/1
- Length of cohabitation: Overnight and removed in morning to check for pregnancy, this was repeated until females were pregnant
- Proof of pregnancy: vaginal plug and sperm in vaginal smear referred to as day 0 of pregnancy
Duration of treatment / exposure:
6 hrs/day
Frequency of treatment:
days 6-15 of gestation
Duration of test:
days 6-15 of gestation
No. of animals per sex per dose:
20
Control animals:
yes, concurrent no treatment

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily
- Cage side observations: mortality, toxicological signs, pharmacological effects

BODY WEIGHT: Yes
- Time schedule for examinations: days 0, 6-15, 21 of gestation

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day #: 21
- Organs examined: uterus, ovaries

Ovaries and uterine content:
The ovaries and uterine content were examined after termination: Yes
Examinations included:
- Gravid uterus weight: No data
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Other: number of live fetuses, number of dead fetuses
Fetal examinations:
- External examinations: Yes: all per litter examined for sex, crown-rump distance, weighed, and malformations
- Soft tissue examinations: Yes: 2/3 per litter examined for gross dissection and examination of viscera, internal sex determination, ureter, kidneys, and heart
- Skeletal examinations: Yes: 2/3 per litter examined for skeletal malformations, and ossification
- Head examinations: Yes: 1/3 per litter examined for neural defects
Statistics:
Analysis was done using the chi-square method, or the F-test and Student's t-test. When the variance differed significantly, the Student's t-test was modified suing Chochran's approximation. The mean number of live fetuses, resorptions, implantations, and corpora lutea were analyzed using the one-tailed t-test.
Indices:
implantation efficiency,

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:no effects

Details on maternal toxic effects:
There was no mortality in either of the dosage groups. Pregnancy rates were comparable between the exposure groups and negative controls. Weight gain was significantly higher in the exposure groups post-dosing. There were no significant clinical observations in either exposure group. The mean number of corpora lutea was significantly decreased in the 300 ppm group. Since ovulation occurred prior to exposure, this was not considered to be treatment related. The mean number of implantations was comparable between exposure groups and negative controls. The implantation efficiency values were actually significantly higher in exposure groups as compared to negative controls. The mean number of live fetuses, resorption sites, and number of dams with more than one resorption site were comparable between exposures and negative controls. The gross postmortem examination of dams showed no treatment related effects.

Effect levels (maternal animals)

Key result
Dose descriptor:
NOAEC
Effect level:
>= 300 ppm
Basis for effect level:
other: Systemic toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
The body weights of fetal males in the 100 ppm group were significantly higher than negative controls. There were some statistically significant differences in mean crown-rump distance between both dosage levels and negative controls, these differences were slight and the effect inconsistant between dosages and sex. These differences were therefore not considered to be indicative of a treatment related effect. Mean numbers of male and female fetuses, and sex ratios were similar between exposure groups and negative controls. Ossification variations were similar in exposure groups and negative controls, as was the incidence of litters with fetuses containing ossification variations. No malformations externally or in the soft tissues were noted in the fetuses except in the positive controls. Though skeletal defects were noted in the exposure group, the types of malformations are common in rat fetus and not considered to be treatment related.

Effect levels (fetuses)

Key result
Dose descriptor:
NOAEC
Effect level:
>= 300 ppm
Based on:
test mat.
Basis for effect level:
other: Developmental Toxicity

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Any other information on results incl. tables

Results - Dams

Endpoint

Negative Control

400 mg/kg ASA

100 ppm

300 ppm

Pregnancy Rate (%)

100.0

95.0

100.0

90.0

Mortality Rate (%)

0.0

10.0

0.0

0.0

Mean Body Weight Gain  (g)

Dams - Days 15-21

84

32

108

103

Mean Corpora Lutea

15.2

14.5

15.5

13.8

Mean No. Implantations

13.0

13.2

13.8

13.2

Implantation Efficiency (%)

85.8

91.1

88.7

95.6

Mean No. Live Fetuses

12.5

7.4

12.9

12.6

Mean No. Dead Fetuses

0.0

0.0

0.0

0.0

Mean No. Resorptions

0.6

5.8

0.9

0.7

Dams with more than one Resorption (%)

10.0

58.8

25.0

11.1

Results – Fetuses

Endpoint

Negative Control

400 mg/kg ASA

100 ppm

300 ppm

Male Mean Fetal Weight (g)

5.57

3.88

5.82

5.62

Female Mean Fetal Weight (g)

5.29

3.62

5.44

5.33

Male Mean Crown-Rump Distance (cm)

4.3

3.7

4.4

4.2

Female Mean Crown-Rump Distance (cm)

4.2

3.6

4.2

4.1

Sex Ratio (%)

91.5

98.4

88.3

105.5

Ossification Variations (%)

70.7

100.0

79.4

79.3

Litters with Ossification Variations (%)

100.0

100.0

95.0

100.0

Soft Tissue Malformations (%)

2.4

26.8

1.1

3.9

Litters with Soft Tissue Malformations (%)

10.0

54.5

5.0

16.7

Gross Evisceration Malformations (%)

5.4

3.6

1.8

4.0

Litters with Gross Evisceration Malformations

25.0

8.3

10.0

16.7

Skeletal Malformations (%)

0.0

21.4

2.9

1.3

Litters with Skeletal Malformations

0.0

66.7

15.0

11.1

Applicant's summary and conclusion

Conclusions:
The NOAEC for developmental toxicity in rats is >=300 ppm (1575 mg/m3) via inhalation. The test substance is also non-teratogenic.
Executive summary:

This study determined the developmental toxicity of MRD-78 -25 in rats exposed via inhalation. Groups of 20 pregnant female rats were exposed 6 hrs/day during days 6 -15 of gestation. Test concentrations of 100 or 300 ppm test substance. In addition to a negative control group, there was also a positive control group that was exposed to acetylsalicylic acid on days 6 -15 of gestation. Dams were observed for toxicological signs and pharmacological effects. On day 21 of gestation, the animals were sacrificed, and examined for corpora lutea and uterine implantation parameters. Fetuses were examined for fetal size, sex ratio, and external, soft-tissue, and skeletal malformations. No adverse effects due to exposure to the test substance were seen in either dams or fetuses. No treatment related malformation effects were noted in the fetuses. The developmental NOAEC for rats by inhalation is >=300 ppm. The test substance is also not teratogenic.