Naphthalene-1,5-diol

Endpoint summary

Key value for chemical safety assessment

Effects on developmental toxicity

Description of key information

Under the condition of this test naphthalene-1,5-diol does not cause developmental toxicity up to and including the highest test dose of 360 mg/kg bw despite maternal toxicity at 360 mg/kg bw/day.

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1987-01-16 to 1987-03-30

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

Test System
Species: Sprague-Dawley CD (outbred, SPF-quality)
Rationale: Specified by the international guidelines as a recommended test system
Source: Charles River, Wiga, D-8741 Sulzfeld 1
Acclimatization: 6 days (minimum) prior to pairing, under test conditions, after veterinary examination
Number of animals: 120 females, 30 per group, 40 males
Initial age: 10 weeks, minimum
Initial body weight: females, approx. 218 - 340 grams, males, about 300 grams
Identification (prior to pairing): Individual cage / animal number tinted on fur with saturated picric acid and tattooed on one ear (numbers)

Husbandry
Conditions
The animals were housed under standard laboratory conditions (Room-no. 12267/12268), Air-conditioned with 10 air changes per hour; the environment was monitored continuously with recording of temperature (range 20 - 24 degrees Centigrade) and relative humidity (range 38 – 60%); 12 hours artificial fluorescent light / 12 hours dark.

Accomodation
The animals were housed in groups of 3 animals prior to the pairing and afterwards the animals were housed individually in Makrolon cages (type Ill) with wire mesh tops and standardized granulated softwood bedding (ARWI-Center, D-4300 Essen).

Diet
Pelleted Altromin diet No. 1324 N spez. (Altromin, D-4937 Lage) ad libitum.
Results of analysis for contaminants are archived in the Archives of the Institute of Toxicology.
Water
Tap water was available ad libitum.
Samples of tap water were examined analytically in regular time intervals. Results of analysis for contaminants are archived in the Archives of the Institute of Toxicology.

Route of administration:

oral: gavage

Vehicle:

other: 1% Carboxymethylcellulose with 0.5% Cremophor in distilled water

Details on exposure:

The test substance was administered orally, by gavage once daily in the morning from day 6 up to day 15 post coitum. All groups received a dose volume of 10 ml/kg body weight, adjusted to the body weight of day 6 post coitum. Control animals were similarly dosed with the vehicle alone.
Rationale
International guidelines recognize the effcacy of oral administration.

Analytical verification of doses or concentrations:

not specified

Details on mating procedure:

Female and male animals were paired in the ratio 3 : 1 from monday 8.00 a.m. to friday 8.00 a.m. .
The day on which spermatozoa were found in the vaginal smear or a vaginal plug was observed was designated day 0 post coitum.
The animals of the second delivery (03/03/87) were paired. The succesfully paired animals replaced non-pregnant rats of the 1st delivery in group 2 and 3.

Duration of treatment / exposure:

From day 6 through to day 15 post coitum

Frequency of treatment:

Once daily

Duration of test:

Up to day 20 post coitum

Dose / conc.:

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

Remarks:

Group 1, females 1 - 30

Dose / conc.:

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

Remarks:

Group 2, females 31 - 60

Dose / conc.:

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

Remarks:

Group 3, females 61-90

Dose / conc.:

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

Remarks:

Group 4, females 91 - 120

No. of animals per sex per dose:

30 pregnant females per dose group.

Control animals:

yes, concurrent vehicle

Details on study design:

The purpose of this study was to assess the effects of 1,5-Dihydroxynaphthalene on embryonic and fetal development in pregnant CD-rats.
Each group consisted of 30 female rats. Investigated were pregnant rats in the group 1 (0 mg/kg) 29, group 2 (20 mg/kg) 20, group 3 (60 mg/kg) 21 and group 4 (360 mg/kg) 24.
1,5-DHN was administered orally by gavage once daily from day 6 to day 15 post coitum. A standard dose volume of 10 ml/kg body weight was used. Control animals were dosed with the vehicle alone.
Females were sacrificed on day 20 post coitum and the fetuses were removed by Caesarean section. The examination of the dams and fetuses was performed in accordance with international recommendations.

Maternal examinations:

The examination of the dams and foetuses was performed in accordancewith international recommendations.

Ovaries and uterine content:

The examination of the dams and foetuses was performed in accordancewith international recommendations.

Fetal examinations:

The examination of the dams and foetuses was performed in accordancewith international recommendations.

Statistics:

The following statistical methods were used.
If the variables could be assumed to follow a normal distribution, the Dunnatt-Test, based on a pooled variance, was applied for the comparison between the treated groups and the control group.
The Steel-Test was applied when the data could not be assumed to follow a normal distribution.
Fisher's Exact test for 2x2 tables was applied if the variables could be dichotomized without loss of information (Bonferroni-Holm-corrected).

Clinical signs:

no effects observed

Description (incidence and severity):

No signs of reaction to the test article administration were observed.

Mortality:

no mortality observed

Description (incidence):

No death occured in the dams of group 1 (vehicle control) and in the test groups 2, 3 and 4.

Body weight and weight changes:

effects observed, non-treatment-related

Description (incidence and severity):

The mean of the body weight gain for the treatment groups compared favourably with the vehicle control values. The mean of the corrected body weight gain in the treatment group 4 was slightly reduced in comparison to the control group, due to a slightly increased mean of the uterus weight of the treatment group 4. Therefore this effect is considered to be incidental.

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

No macroscopic changes were noted in the dams of all groups at terminal necropsy.

Other effects:

no effects observed

Description (incidence and severity):

No significant differences were noted between the mean reproduction data of the vehicle control group and the treatment groups, which were considered to be an effect of treatment with the test article.

Details on maternal toxic effects:

The dams tolerated the applied dose of up to 360 mg/kg bw without lethality or symptoms of cumulative intoxication.
But , the corrected mean body weight gain of the high dose group was significantly decreased compared to the control animals. However, at 20 mg/kg bw, a similar increase in mean uterus weight was not associated with a change of the corrected mean body weight.
There were no treatment related effects in the gestation data.

Dose descriptor:

NOAEL

Effect level:

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

Basis for effect level:

other: maternal toxicity

Dose descriptor:

NOAEL

Effect level:

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

Basis for effect level:

other: developmental toxicity

Fetal body weight changes:

no effects observed

Description (incidence and severity):

Group mean and litter mean body weights of the fetuses were similar in the dose groups and the control group.

Changes in sex ratio:

no effects observed

Description (incidence and severity):

The sex ratio of the fetuses was not affected by the treatment wi th the test substance.

External malformations:

no effects observed

Description (incidence and severity):

No abnormal findings were no ted at external examination of fetuses which were considered to be an effect of treatment with the test substance. In the group 1 (control) one fetus exhibited exentery and in the group 4 two cases of hydrops were recorded.

Skeletal malformations:

effects observed, non-treatment-related

Description (incidence and severity):

No test article related abnormal findings were noted at skeletal examination of the fetuses.
The level of skeletal variations in fetuses of the control and the treatment groups was similar. The test group 3 exhibited an increased number of dumbbell shaped ventral segments of thoracic vertebrae that was considered as incidental.
The level of skeletal ossification in fetuses of all groups was considered to be similar.
The isolated statistically significant differences in incomplete ossified skull bones, non ossified hyoid, two or several sternebrae in the treatment groups were considered to be incidental because this retardation effects were not accompanied by weight retardation of the fetuses of the treatment groups. The incidental character of these retardations is emphasized by the fact that the values were within the normal range of variation for this rat strain (4).

Visceral malformations:

effects observed, non-treatment-related

Description (incidence and severity):

Following fetuses showed blood in abdominal cavity as a main finding:
Group I. One out of 123 examined fetuses
Group 2: One out of 84 examined fetuses
Group 3. One out of 85 examined fetuses
Group 4. Three out of 105 examined fetuses
In all other fetuses examined no abnormalities were discovered.

Dose descriptor:

NOAEC

Effect level:

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

Basis for effect level:

changes in sex ratio

fetal/pup body weight changes

skeletal malformations

visceral malformations

Developmental effects observed:

no

Lowest effective dose / conc.:

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

Conclusions:

The results of this study show that repeated oral administration (day 6 - day 15 post coitum) of 1,5 - DHN to pregnant rats caused no symptoms of cumulative toxicity at a dose level of 360 mg/kg body weight/day and less.
There were no observable effects on maternal behaviour, body weight gain, implantations, number of live fetuses, litter range and post implantation loss due to the treatment with the test substance.
The number of corpora lutea end the number of implantations was high in dams of all groups, as weIl as the mean of fetuses per litter, litter weights of fetuses.
The number and type of skeletal variations and skeletal retardations were not affected by treatment with 1,5 - DHN.
On the basis of the described results, the test substance 1,5 - DHN is not cumulative toxic to pregnant rats and does not reveal any embryotoxic or teratogenic potential at dose levels up to 360 mg/kg body weight/day.

Executive summary:

The purpose of this study was to assess the effects of 1,5 – Dihydroxynaphthalene on embryonic and fetal development in pregnant CD-rats.

Each group consisted of 30 female rats. Investigated were pregnant rats in the group 1 (0 mg/kg) 29, group 2 (20 mg/kg) 20, group 3 (60 mg/kg) 21 and group 4 (360 mg/kg) 24.

1,5 - DHN was administered orally by gavage once daily from day 6 to day 15 post coitum. A standard dose volume of 10 ml/kg body weight was used. Control animals were dosed with the vehicle alone.

Females were sacrificed on day 20 post coitum and the fetuses were removed by Caesarean section. The examination of the dams and fetuses was performed in accordance with international recommendations.

The dams tolerated the applied dose of up to 360 mg/kg 1,5 - DHN without lethality or any symptoms of cumulative intoxication.

Throughout the gestation the mean body weight gain of the test animals compared favourably with the control animals.

There were no treatment related effects in the reproduction data.

The examined fetuses showed no treatment related malformations.

The level of skeletal variations in test and control group was considered to be similar.

The level of skeletal ossification in fetuses of all groups was considered to be within normal range.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

360 mg/kg bw/day

Justification for classification or non-classification

Under the condition of this test naphthalene-1,5-diol does not cause developmental toxicity up to and including the highest test dose of 360 mg/kg bw despite maternal toxicity at 360 mg/kg bw/day.