Ammonium hydrogendifluoride

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: High quality NTP study

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

publication

Title:

Technical Report on the Toxicology and Carcinogenesis Studies of Sodium Fluoride in F344/N Rats and B6C3F, Mice.

Author:

NTP

Year:

1990

Bibliographic source:

U.S Department of Health and Human Services. NTP TR 393, NIH Publication No. 91-2848, December 1990

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)

Principles of method if other than guideline:

Assessment of Sister Chromatid Exchange (SCE) and chromosomal aberration.

GLP compliance:

not specified

Type of assay:

in vitro mammalian chromosome aberration test

Test material

Test material information

Constituent 1

Reference substance name:

Sodium fluoride

EC Number:

231-667-8

EC Name:

Sodium fluoride

Cas Number:

7681-49-4

IUPAC Name:

sodium fluoride

Details on test material:

Sodium fluoride

Method

Target gene:

Not relevant

Species / strain

Species / strain / cell type:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Metabolic activation system:

Aroclor 1254-induced male Sprague-Dawley rat liver S9 and cofactor mix.

Test concentrations with justification for top dose:

In each trial, 5 different concentrations of sodium fluoride were tested in the range 1.6 to 1600 µg/mL.

Vehicle / solvent:

No vehicle used.

Controls

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Details on test system and experimental conditions:

Sodium chloride was tested in cultured Chinese Hamster ovary (CHO) cells for induction of sister chromatid exchanges (SCE) and chromosomal aberrations (Abs) both in the presence and absence of Aroclor of Aroclor 1254 induced male Sprague-Dawley rat liver S9 and cofactor mix. Cultures were handled under gold lights to prevent photolysis of bromodeoxyuridine substituted DNA. Below gives the test system ad conditions used for each trial:

1. In the SCE test without S9, CHO cells were incubated for 26 hours with the study chemical in McCoy's 5A medium supplemented with 10% fetal bovine serum, l-glutamine (2 mM) and antibiotics Bromodeoxyuridine (BrdU) was added 2 hours after culture initiation. After 26 hours, the medium containing the chemical was removed and replaced with fresh medium plus BrdU and Colcemid and incubation was continued for 2 more hours. Cells were then harvestedby mitotic shake off, fixed and stained with Hoechst 33258 and Giemsa.

2. In the SCE test with S9, cells were incubated with the chemical, serum-free medium and S9 for 2 hours. The medium was then removed and replaced with medium containing BrdU and no test chemical and incubation continued for an additional 26 hours, with Colcemid present for the final 2 hours. Harvesting and staining was the same for cells treated without S9.

3. In the Abs test without S9, cells were incubated in McCoy's 5A medium with the study chemical for 8 hours; Colcemid was added and incubation continued for 2 hours. The cells were harvested by mitotic shake off, fixed and stained with Giemsa.

4. In the Abs test with S9, cells were treated with the study chemical and S9 for 2 hours, after which the treatment medium was removed and the cells incubated for 10 hours in fresh medium with Colcemid present for the final 2 hours. Cells were harvested in the same manner as for treatment without S9.

Evaluation criteria:

Statistical analysis were conducted on both the slopes of the dose response curves and the individual dose points. An SCE frequency 20% above the concurrent solvent control value was chosen as a statiscally conservative positive response. If one dose point was positive, the chemical was termed 'weak positive'; if two or more dosesw ere positive, the chemical was judged 'positive.' Abs data was presented as percentage of cells with aberrations. As with SCE, both the dose-response curve and individual dose points were statistically analysed. A statistically significant (P<0.003) effect on the slope of the curve or on at least two dose points (P<0.05) was sufficient for a conclusion of positive for a test.

Statistics:

See above in evaluation criteria.

Results and discussion

Test results

Species / strain:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Genotoxicity:

ambiguous

Remarks:

: see discussion below

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Any other information on results incl. tables

Conflicting results were found in the two laboratories testing sodium fluoride on CHO cells for any cytogenetic effects. SCEs were induced in one laboratory at doses of 66.7 and 75 µg/mL without S9 and at doses of 1200 µg/mL and higher with S9. In two of the five cases, the positive results were seen following delayed harvest to allow cells, whose division time was inhibited by the higher doses of sodium fluoride to progress to the second metaphase division to the point where the cells could be scored. The laboratory reporting negative SCE results did not employ extended harvest times and was able to test up to only 50 µg/mL sodium fluoride without S9 and 500 µg/mL with S9. In the tests for the induction of Abs, positive results were reported in one laboratory at doses of 400 µg/mL sodium fluoride and greater without S9. The second laboratory reported negative results without S9, but the highest dose tested was 200 µg/mL. Neither laboratory showed a reproducible increase in chromosomal aberration in the presence of S9.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information):
ambiguous

The results are inconclusive. The two laboratories used to test the effects of sodium fluoride on CHO cells showed conflicting results; one reported a negative result and one reported a positive result for both induction of sister chromatid exchanges (SCE) and chromosomal aberrations (Abs).

Executive summary:

The results are inconclusive. The two laboratories used to test the effects of sodium fluoride on CHO cells showed conflicting results; one reported a negative result and one reported a positive result for both induction of sister chromatid exchanges (SCE) and chromosomal aberrations (Abs).