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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Published, guideline-comparable GLP study

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
2001

Materials and methods

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

Test material

Constituent 1
Reference substance name:
Ammonium perchlorate
EC Number:
232-235-1
EC Name:
Ammonium perchlorate
Cas Number:
7790-98-9
IUPAC Name:
ammonium perchlorate
Details on test material:
Ammonium perchlorate (CAS No. 7790-98-9), purity: 99.8%, obtained from Aldrich Chemical Company, Inc., lot 03907LF.
A read-across is proposed because ammonium perchlorate will dissociate in aqueous solutions to give ammonium and perchlorate ions.

Test animals

Species:
rabbit
Strain:
New Zealand White
Details on test animals or test system and environmental conditions:
The animals was naturally bred New Zealand White [Hra:(NZW)SPF] rabbits, supplied by Covance Research Laboratories, Inc. Rabbits were randomly assigned to treatment groups, based on body weight. Each rabbit was provided with 150 g feed (Certified Rabbit Chow #5322) pre-exposure, and 180 g during the exposure. Rabbits were given ab libitum access to water (untreated or treated).
Housing conditions were not specified in the paper, but were reported to be in compliance with the Guide for the Care and Use of Laboratory Animals.

Administration / exposure

Route of administration:
oral: drinking water
Vehicle:
unchanged (no vehicle)
Details on exposure:
Test formulations of ammonium perchlorate in deionised water were prepared at least weekly, stored refrigerated, and dosage solutions were brought to room temperature prior to use. Test drinking solutions were adjusted to concentrations that yielded target doses of 0, 0.1, 1.0, 10.0, 30.0 and 100.0 mg/kg/day based on actual weekly water consumption. The ammonium perchlorate was considered 100% active for the purpose of dose calculations. Rabbits were given ad libitum access to the water.
Analytical verification of doses or concentrations:
not specified
Details on analytical verification of doses or concentrations:
Test solutions were adjusted based on actual water consumption, but no further information regarding analytical verification of doses is given.
Details on mating procedure:
Naturally bred by the supplier - no further information is given in the paper.
Duration of treatment / exposure:
Gestational days (GD) 6 to 28 (23 days)
Frequency of treatment:
Daily - ad libitum access to drinking water
Duration of test:
23 days; does were sacrificed on gestational day 29.
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 0.1, 1.0, 10.0, 30.0 and 100.0 mg/kg/day
Basis:
nominal in water
No. of animals per sex per dose:
25 rabbits per group
Control animals:
yes
Details on study design:
Rabbits were randomly allocated to treatment groups based on body weights. Doses were selected on the basis of dose-finding study carried out by Argus Laboratories, where thyroid histopathology was evident in New Zealand White rabbits at doses of 20, 50 and 100 mg/kg/day. T3 (triiodothyronine), T4 (thyroxine) and TSH (serum thyroid stimulating hormone) blood levels were reduced at all doses and three malformed foetuses from three litters in the 20 mg/kg/day dose group were observed at gross external examination.
Controls (0 mg/kg/day) received deionised water only.

Examinations

Maternal examinations:
All rabbits were observed for viability at least twice daily, and for general appearnce at least one during the pre-exposure period. The rabbits were also examined daily during the exposure period and on the day of sacrifice (GD 29) for clinical observations of toxicity, abortions, premature deliveries, and deaths. Body weights, feed and water consumption values were recorded daily.
Blood samples were collected under anaesthesia on GD 29 for determination of TSH, T3 and T4 levels. Rabbits were then sacrificed and subjected to gross necropsy of the thoracic, abdominal and pelvic viscera. A section of the trachea containing the thyroids/parathryroids of all rabbits was excised. Following fixation the thyroid/parathyroid tissue samples were carefully trimmed, weighed, and evaluated histologically by a veterinary pathologist.
Ovaries and uterine content:
The number of corpora lutea in each ovary was recorded. The uterus was excised and examined for pregnancy, number and distribution of implantations, early and late resorptions, and live and dead foetuses.
Fetal examinations:
Each caesarean-delivered foetus was weighed and examined for gross external alterations. All foetuses were examined by dissection and the brain was examined in situ for approximately one-half of the foetuses in each litter. The remaining foetuses in each litter were decapitated and the heads were examined using Wilson's sectioning technique. All foetuses were examined for skeletal and cartilaginous alterations.
Statistics:
Variance test for homogeneity of the binomial distribution was used for clinical observations and proportion data. Bartlett's test of homogeneity of variances and ANOVA was used for continuous data, followed by Dunnett's test (or Dunn's method of multiple comparisons where K-W was used). If ANOVA wasn't appropriate, the Kruskal-Wallis test was used when 75% or fewer ties were present, but when more than 75% ties were present Fisher's Exact Test was used.
Indices:
Not calculated
Historical control data:
No information available

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
There were no treatment-related deaths. Two does in the 1 mg/kg group aborted on GD 28 and were sacrificed. Both abortions were considered unrealted to treatment because the incidences were not dose-dependent. One dam in the 100 mg/kg group prematurely delivered on GD 27. Because rabbits normally deliver on GD 31, and the pups appeared to be full term (they had fur and were nursing), it was assumed that the rabbit had been incorrectly identified and shipped by the supplier on the wrong day of gestation.
Clinical observations included localised alopecia, ungroomed coat, scant soft or liquid faeces, and a red perivaginal, perinasal or perioral substance. The clinical observations recorded were considered unrelated to treatment because the incidences were not dose-dependent; the observation was associated with abortion of a litter, and/or the observations were commonly seen in rabbits in the laboratory environment.
The maternal body weights in the control group were consistently lower than the treated groups over the gestation period. There were however, no statistically significant differences in average maternal body weights, gravid uterine weights, body weight gains, or corrected GD29 body weights (GD29 bodyweight minus the gravid uterine weight) among exposure groups during gestation.
The only adverse necropsy observation was a mottled liver that occurred in the 1 mg/kg group doe that aborted.
Microscopic examination of the dams' thyroid glands revealed hypertrophy of the follicular epithelium in the 10, 30 and 100 mg/kg groups, this was considered to be treatment related by the authors. No treatment related microscopic changes were observed in the thyroid gland of any rabbits from the 0.1 or 1.0 mg/kg groups. In the affected thyroids, there was an increased height or enlargement of the follicular epithelium, occasionally resulting in a decrease in the lumen of follicles, which contained pale and occasionally vacuolated colloid.
Serum T4 levels appeared to decrease in a treatment-related manner, with the 30 and 100 mg/kg groups showing statistically significant decreases compared to controls. This decrease was considered to be treatment-related by the authors because it corresponded to the hypertrophy of follicular epithelium. There were no statistically signficant changes in serum T3 and TSH in treated rabbits compared to controls.

Effect levels (maternal animals)

open allclose all
Dose descriptor:
NOAEL
Effect level:
100 mg/kg bw/day (nominal)
Basis for effect level:
other: developmental toxicity
Dose descriptor:
NOAEL
Effect level:
1 mg/kg bw/day (nominal)
Basis for effect level:
other: maternal toxicity

Results (fetuses)

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

Details on embryotoxic / teratogenic effects:
Caesarean section observations were based on 22, 24, 23, 24 and 23 pregnant does surviving to GD 29. There were no effects on caesarean sectioning or litter parameters. All values were within laboratory historical ranges. All placentae appeared normal and no dam had a litter consisting of only resorbed conceptuses. Litter averages for corpora lutea, implantations, litter sizes, live and dead foetuses, percent dead or resorbed conceptuses, and foetal body weights were comparable and did not differ significantly between groups.
Foetal evaluations were based on 180, 184, 196, 195, 189 and 206 live foetuses in the six exposure groups, respectively. No foetal alterations were attributable to treatment. Only 6 foetuses had gross external alterations: 3 from the control group and two from the 1 mg/kg group, and 1 from the 100 mg/kg group litters. Foetal soft tissue alterations only occurred in four foetuses of the control group, two in the 0.1 mg/kg group, three in the 1 mg/kg groups, two in the 30 mg/kg group and five in the 100 mg/kg group.
A statistically significant difference in incidence of folded retina was observed; the foetal incidence in all the treated groups was lower than the control group. Folded retina of the right and/or left eye occurred in several foetuses, but was only seen in the heads examined with Wilson;s technqieu and was therefore considered to be an artefact of processing. Foetuses in some of the exposure groups showed significant increases in skeletal alterations, however none of the changes were considered to be treatment-related as there was no evidence of a dose-response relationship.

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Any other information on results incl. tables

Actual consumed doses of ammonium perchlorate on GDs 6 to 19 were 0, 0.1, 1.0, 10.8, 33.9 and 114.2 mg/kg/day. During GDs 19 to 29, actual consumed doses of ammonium perchlorate were 0, 0.1, 0.8, 10.0, 26.7 and 90.4 mg/kg/day. Therefore, average actual consumed doses for the entire period of gestation were 0, 0.1, 0.9, 10.4, 30.3 and 102.3 mg/kg/day.

Applicant's summary and conclusion

Conclusions:
There was no evidence that ammonium perchlorate is toxic to the developing foetus. An increased incidence of thyroid follicular hypertrophy was observed in does, however the thyroid is a target organ for the perchlorate ion therefore this effect is not attributed to the ammonium ion.
Executive summary:

This developmental toxicity study was conducted to evaluate the embryo-foetal toxicity and teratogenic potential of ammonium perchlorate in New Zealand White [Hra:(NZW)SPF] rabbits. Pregnant rabbits were given continual access to ammonium perchlorate in drinking water at target doses of 0, 0.1, 1.0, 10.0, 30.0, and 100.0 mg/kg/day on gestation days 6 through 28. The actual consumed doses in the study were 0, 0.1, 0.9, 10.4, 30.3, and 102.3 mg/kg/day. The rabbits were sacrificed on gestation day 29, and foetuses were examined for developmental alterations. In addition, blood was collected from does for determination of serum thyroid stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4) levels and the thyroid was subjected to histopathologic examination. No maternal deaths were attributed to perchlorate exposure. Ammonium perchlorate as high as 100.0 mg/kg-day did not affect caesarean sectioning or litter parameters studied, and all values were found to be within the historical ranges of the laboratory. The litter averages for corpora lutea, implantations, litter sizes, live and dead foetuses, percent dead or resorbed conceptuses, and fetal body weights were comparable and also did not differ significantly in the six dose groups. All placentae appeared normal and no dam had a litter consisting of only resorbed conceptuses. The maternal thyroid was the target organ for ammonium perchlorate in this study. Increased incidence of thyroid follicular hypertrophy was observed in does treated with 10 mg/kg/day and above, and significantly decreased T4 was observed in does treated with 30 mg/kg/day and above. Based on these data, the maternal no-observable-adverse-effect level (NOAEL) for ammonium perchlorate was 1.0 mg/kg-day. The developmental NOAEL for ammonium perchlorate was found to be 100.0 mg/kg-day for rabbits.