Ammonium carbonate

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: Documentation insufficient for assessment. Very few of the parameters measured in a guideline test were monitored in this study. The volume injected and vehicle is unknown. Only two animals were used in each exposure group.

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1976

Materials and methods

Principles of method if other than guideline:

Four drugs— trypan blue, urethane, cyclophosphamide and methotrexate- were administered i.p. into pregnant mice on the 7th to 9th day of gestation.

GLP compliance:

no

Remarks:

(the study as executed before the existence of GLP)

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Sodium hydrogencarbonate

EC Number:

205-633-8

EC Name:

Sodium hydrogencarbonate

Cas Number:

144-55-8

IUPAC Name:

sodium hydrogen carbonate

Test material form:

other: liquid

Details on test material:

Analytical purity: no data

Test animals

Species:

mouse

Strain:

Swiss

Details on test animals or test system and environmental conditions:

Species: Mouse: swizz albino
Source: no data
Number per sex: 127 females, 12 males
Stage of pregnancy at test initiation: 7 weeks

Administration / exposure

Route of administration:

intraperitoneal

Vehicle:

not specified

Details on exposure:

VEHICLE
- Concentration in vehicle: 2 %.

Analytical verification of doses or concentrations:

no

Details on mating procedure:

The breeding groups consisted of six females and two males in each cage, females were examined in the morning and afternoon for evidence of mating. Females with fresh vaginal plugs were isolated and the date noted as the first day of pregnancy.

Duration of treatment / exposure:

The mice were exposed i.p. on day 7, 8 and 9 of pregnancy, and sacrificed on day 14 of the pregnancy.

Frequency of treatment:

Daily

Duration of test:

7 days

Doses / concentrations

Remarks:

Doses / Concentrations:
2% NaHCO3
Basis:
nominal conc.

Control animals:

yes

Details on study design:

In this study the NaHCO3 group of animals was considered a control group together with a group receiving saline and an untreated group.

Examinations

Maternal examinations:

- Histopathology P: Animals (P) were killed on the fourteenth day of pregnancy, and the uteri removed. The uterus was examined for implantation sites, viable fetuses and resorption sites.

Fetal examinations:

Viable foetuses (F1) were examined for grossly visible malformations. Histological preparations were made of selected foetuses.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Details on maternal toxic effects:
- Gross pathology incidence and severity: There were 2 resorption sites in total in the two females, compared to 2 resorption sites in 3 saline treated controls.
- Number of implantations: 22
- Litter size and weights: There were 20 viable foetuses in total from two females. In the control groups 27 foetuses were counted in 3 saline treated females, and 17 foetuses in 2 untreated females.

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Details on embryotoxic / teratogenic effects:
In the NaHCO3 group, hematomas were found in 4 foetuses (of a total of 20); no other abnormalities were found. The increased incidence of hematomas may be incidental, as in the groups tested with a drug (the only which 2% NaHCO3 was added to), hematomas were also observed. No abnormalities were observed in the other control groups.

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Observations of control females:

Except for hematoma formation observed in four fetuses from females injected with 2% NaHCO3 solution, no gross abnormalities were detected among the fetuses.

Frequency of embryo lethality and gross abnormalities:

More resorption sites were observed among the experimental groups than the 6% in the control group. Successful implantations and viable fetuses were greatly reduced with methotrexate (28%), cyclophosphamide (58%), and trypan blue (62%) treatments and to a lesser extent with urethane (74%). Gross externally visible defects were generally not observed except in the case of cyclophosphamide, where microencephaly (abnormally small cerebral hemispheres) occurred in 3 of 21 viable fetuses. Multiple hematomas were found on 5 of 8 fetuses of the methotrexate group and 4 of 20 fetuses in the NaHCO3-treated controls.

Microscopic examination of the fetuses:

Three fetuses from the methotrexate group were indistinguishable from the controls. The three microencephalic fetuses of the cyclophosphamide group were retarded in neural development but appeared otherwise to be histologically well differentiated. Four of five fetuses in the trypan blue group and one of the two fetuses of the urethane group, despite their superficially normal appearance, revealed obvious internal degenerative changes when examined microscopically. In the trypan blue group the basic neural organization was maintained but the tissues were clearly undergoing degenerative changes. The damage was more extensive in the brain region than posteriorly. The surrounding tissues and especially the mesenchyme were sparse. One fetus in the urethane group was normal and the other obviously morbid. In the latter the mesenchyme was overabundant and the cells were atypically rounded and clumped. The cells of the neural epithelium were few in number and loosely and abnormally arranged. The neural epithelium was generally thin, often discontinuous, and thrown into numerous irregular folds.

Applicant's summary and conclusion

Conclusions:

The four drugs were found to be detrimental to the embryos when administered to pregnant females during the sensitive period in the morphogenesisof the nervous system.

Executive summary:

Four drugs— trypan blue, urethane, cyclophosphamide and methotrexate— were tested to ascertain their deleterious effects on the

neural development of the mouse embryo. The drugs were administered i.p. into pregnant females on the 7th to 9th day of gestation. The

animals were sacrificed on the 14th day and gross and microscopic examinations of the uterine contents were made. From counts of viable fetuses and resorption sites all four drugs appeared to increase fetal mortality, methotrexate the most, and urethane the least. Within the range of the drug dosage tested only cyclophosphamide treatment resulted in grossly visible neural defects; however, microscopic examination of representative fetuses in the trypan blue and urethane treatment groups revealed histologically obvious degenerative alterations. Methotrexate-treated fetuses appeared to be unaffected.