Pentane

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1996-07-25 to 1997-04-11

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: This study is classified as reliable without restriction because it is was performed according to GLPs and in compliance with OECD principles 414.

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1997

Report date:

1997

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.31 (Prenatal Developmental Toxicity Study)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Pentane

EC Number:

203-692-4

EC Name:

Pentane

Cas Number:

109-66-0

Molecular formula:

C5H12

IUPAC Name:

pentane

Details on test material:

- Name of test material (as cited in study report): n-pentane
- Substance type: C5 aliphatic
- Physical state: liquid
- Analytical purity: 97.4% (considered pure for purpose of dosing)
- Lot/batch No.: 2036924
- Expiration date of the lot/batch: June 2001
- Stability under test conditions: 7 days at 2% and 20% w/v
- Storage condition of test material: refrigerated

Test animals

Species:

rat

Strain:

other: Crl:CD BR VAF/Plus

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc., Portage, Michigan
- Age at study initiation: 14 to 16 weeks (females)
- Weight at study initiation: 243 to 316 grams (females)
- Fasting period before study: no
- Housing: individually-housed except during mating in suspended stainless-steel, wire mesh cages
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 20 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 to 24
- Humidity (%): 40 to 70
- Air changes (per hr): not reported
- Photoperiod (hrs dark / hrs light): 12 hours light and 12 hours dark

- IN-LIFE DATES: From: 1996-10-07 To: 1996-11-08

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: Test material formulations were prepared weekly by mixing appropriate amounts of test material with vehicle; test-material formulations were divided into individual samples for each day and stored in a refrigerator until needed.

VEHICLE
- Justification for use and choice of vehicle (if other than water): test material was soluble in carrier
- Concentration in vehicle: not reported
- Amount of vehicle (if gavage): not reported
- Lot/batch no. (if required): not reported
- Purity: not reported

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Test material formulations were evaluated for stability, homogeneity, and achieved concentration. Stability and homogeneity were evaluated prior to the start of the study as part of the dose-range finding study (Study no. 157533; achieved concentration was evaluated on the first and third dosing mixture preparations. Results from the dose-range finding study indicate that the test material formulations were stable for at least 7 days at 2% and 20% w/v and homogenous (with the relative standard deviation being 1% for both sample sets). Test material formulations were found to be within 16% of the nominal concentration.

Details on mating procedure:

- Impregnation procedure: [artificial insemination / purchased timed pregnant / cohoused]: cohoused
- If cohoused:
- M/F ratio per cage: 1:1
- Length of cohabitation: not reported
- Females were placed in cage with male. After confirmation of mating, each female was returned to its own cage. New females were then placed in the males' cages until the required number of mated females was obtained by continuous cohabitation in consideration of lab scheduling.
- Further matings after two unsuccessful attempts: not reported
- Verification of same strain and source of both sexes: yes
- Proof of pregnancy: vaginal plug and/or sperm in vaginal rinse referred to as day 0 of pregnancy

Duration of treatment / exposure:

gestation day (gd) 6 though 15

Frequency of treatment:

daily

Duration of test:

IN-LIFE DATES: From: 1996-10-07 To: 1996-11-08

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 100, 500, or 1000 mg/kg/day
Basis:
nominal conc.
Dosing volumes were 5 mL/kg and based on the most recent individual body weights

No. of animals per sex per dose:

25 dams per group

Control animals:

yes

Details on study design:

- Dose selection rationale: A dose-range finding study (Study no. 157533), in which rats were dosed with n-pentane via gavage at levels of 0, 250, 500, 750, and 1000 mg/kg. Maternal signs of toxicity were observed at 1000 mg/kg and included decreased body weight gain and food consumption over the treatment period and overall gestation interval; no other signs of toxicity were observed in dams or fetuses.
- Rationale for animal assignment (if not random): Mated females were assigned to dose groups in the order of mating.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: At least twice daily during treatment and at least once daily at other times during the study

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily during gestation

BODY WEIGHT: Yes
- Time schedule for examinations: gd 0, 6, 9, 12, 15, 18, and 21

FOOD CONSUMPTION: Yes
- Time schedule for examinations: gd 0, 6, 9, 12, 15, 18, and 21

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 21
- Organs examined: Ovaries

OTHER: Surviving dams and those that delivered prior to scheduled necropsy were scarified by carbon dioxide asphyxiation and exsanguination. Dams that delivered prior to scheduled necropsy were examined for gross lesions, and the number of implantation sites or concepti in each horn was counted. Surviving dams were necropsied, and uterine weight with ovaries attached was recorded. Uteri of all non-pregnant females were stained with ammonium sulfide to confirm pregnancy status.

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
- Other: location of implantations

Fetal examinations:

- External examinations: yes: all per litter (number of live and dead fetuses was counted; fetuses were weighed, sexed, and examined for gross malformations)
- Soft tissue examinations: yes: half per litter
- Skeletal examinations: yes: half per litter
- Head examinations: yes: half per litter

Statistics:

Statistical methods used are presented in the table below. Statistical evaluation of equality of means was conducted by a one-way analysis of variance and a test for ordered response in dose groups. Equal variances were evaluated by Bartlett's test. Equal variances were then tested using parametric methods, otherwise nonparametric techniques were used. Percentages, where appropriate, were calculated and transformed by Cochran's transformation, followed by the arc sine transformation. Both raw and transformed percentages were tested for statistical significance. The Bartlett's test was conducted at the 1% level of significance; all other tests were conducted at the 5% and 1% level of significance.

Indices:

preimplantation loss
postimplantation loss

Historical control data:

not provided

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 were no treatment-related changes in mean body weight, body weight gain, uterine weight, corrected body weight, food consumption, or uterine implantation data. There were no treatment-related mortalities or clinical signs of toxicity.

Effect levels (maternal animals)

1

Key result

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day

Basis for effect level:

other: maternal toxicity

2

Key result

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day

Basis for effect level:

other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
There were no treatment-related changes in growth or increased fetal death. There were no changes in total malformations or variations.

Effect levels (fetuses)

Key result

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day

Basis for effect level:

other: There were no signs of developmental toxicity observed during this study.

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Key result

Developmental effects observed:

no

Any other information on results incl. tables

^a Data obtained from pages 28 -29 in the study report.

Cesarean section observations^a
Observation	Dose (mg/kg bw/day)
	0	100	500	1000
No. Animals assigned (mated)	25	25	25	25
No. Animals pregnant	24	25	23	25
Pregnancy rate (%)	96	100	92	100
No. Nonpregnant	1	0	2	0
Maternal wastage
No. died	0	0	0	0
No. Died pregnant	0	0	0	0
No. Died nonpregnant	0	0	0	0
No. Aborted	0	0	0	0
No. Premature delivery	1	1	0	0
Corpora lutea/Dam	15.26±1.63	15.88±1.68	15.43±1.78	15.68±2.21
Implantations/Dam	14.52±1.70	14.88±2.33	14.83±1.83	15.16±2.32
Total No. litters	23	24	23	25
Total number of live fetuses Live fetuses/Dam	310 13.48±1.78	346 14.42±2.26	318 13.83±2.19	359 14.36±2.29
Total number of dead fetuses Dead fetuses/Dam	0 0.0±0.0	0 0.0±0.0	0 0.0±0.0	0 0.0±0.0
Total No. resorptions	24	11	23	19
Early	22	11	23	18
Late	2	0	0	1
Resorptions/Dam	1.04±0.98	0.46±0.59	1.00±0.95	0.76±0.83
Early	0.96±0.98	0.46±0.59	1.00±0.95	0.72±0.84
Late	0.09±0.29	0.0±0.0	0.0±0.0	0.04±0.20
Litters with total resorptions	0	0	0	0
Mean fetal weight (g)	0	0	0	0
Males	5.34±0.38	5.45±5.40	5.40±0.44	5.42±0.46
Females	5.13±0.40	5.12±0.37	5.21±0.37	5.14±0.55
Sex ratio (% male)	49	49	47	50
Preimplantation loss (%)	4.6±7.8	6.3±12.5	4.0±5.3	3.5±4.7
Postimplantation loss (%)	7.1±6.5	3.0±3.7	7.0±7.0	5.3±5.6

^a Data obtained from pages 32 -34 and 73 -167 in the study report.

 

External examinations^a
Observations^b	Dose (mg/kg bw/day)
	0	100	500	1000
No. Fetuses (litters) examined	309 (23)	346 (24)	318 (23)	359 (25)
No. Fetuses (litters) affected with variations	0 (0)	0 (0)	0 (0)	0 (0)
No. Fetuses (litters) affected with malformations	0 (0)	0 (0)	1 (1)	1 (1)

^a Data obtained from pages 35 in the study report.

^b Some observations may be grouped together.

^c Fetal (litter) incidence

 

Visceral examinations^a
Observations^b	Dose (mg/kg bw/day)
	0	100	500	1000
No. Fetuses (litters) examined	156 (23)	172 (24)	161 (23)	178 (25)
No. Fetuses (litters) affected with variations	0 (0)	3 (2)	2 (2)	1 (1)
No. Fetuses (litters) affected with malformations	4 (3)	7 (4)	2 (2)	9 (6)

^a Data obtained from page 35 in the study report.

^b Some observations may be grouped together.

^c Fetal (litter) incidence

 

Skeletal examinations^a
Observations^b	Dose (mg/kg bw/day)
	0	100	500	1000
No. Fetuses (litters) examined	154 (23)	174 (24)	157 (23)	181 (25)
No. Fetuses (litters) affected with variations	27 (14)	31 (13)	25 (13)	44 (17)
No. Fetuses (litters) affected with malformations	0 (0)	0 (0)	1 (1)	0 (0)

^aData obtained from page 35 in the study report.

^bSome observations may be grouped together.

^cFetal (litter) incidence

 

Applicant's summary and conclusion

Conclusions:

There were no signs of maternal toxicity at any dose level. There were no treatment-related changes in mean body weight, body weight gain, uterine weight, corrected body weight, food consumption, or uterine implantation data. There were no treatment-related mortalities or clinical signs of toxicity. The maternal NOAEL is 1000 mg/kg/day.

There were no signs of developmental toxicity at any dose level. There were no treatment-related changes in growth or increased fetal death. There were no changes in total malformations or variations. The developmental NOAEL is 1000 mg/kg/day.

Executive summary:

In a developmental toxicity study, n-pentane was orally administered via gavage to 25 Crl:CD BR VAF rats per dose at dose levels of 0, 100, 500, or 1000 mg/kg bw/day from days 6 through 15 of gestation.  There were no signs of maternal toxicity at any dose level.  There were no treatment-related changes in mean body weight, body weight gain, uterine weight, corrected body weight, food consumption, or uterine implantation data.  There were no treatment-related mortalities or clinical signs of toxicity.  A maternotoxic dose was not used.  However, the highest dose tested was 1000 mg/kg/day, and no adverse effects were observed.  In general, the highest dose tested does not need to exceed 1000 mg/kg/day unless potential human exposure data indicate the need for higher doses.  Therefore, the study reported a maternal NOAEL of 1000 mg/kg/day.  

 

There were no signs of developmental toxicity at any dose level. There were no treatment-related changes in growth or increased fetal death. There were no changes in total malformations or variations. The developmental NOAEL is 1000 mg/kg/day.

 

This study received a Klimisch score of 1 and is classified as reliable without restriction because it was performed according to GLPs and in compliance with OECD principles 414.