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Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information
In two laboratories, sodium fluoride was tested for induction of trifluorothymidine resistance in mouse L5178Y lymphoma cells; results were positive both with and without S9.
Link to relevant study records
Reference
Endpoint:
in vitro gene mutation study in mammalian cells
Remarks:
Type of genotoxicity: gene mutation
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
1987
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Study reviewed by the United States Governmental Organisation "NATIONALTOXICOLOGY PROGRAM" (NTP), U.S. DEPARTMENT OF HEALTH AND HUMANSERVICES, PublicHealthService, National Institutes of Health.Therefore it is consired as reasonably reliable. Study done according to OECD Guideline. Read across justification is given in section 13 assessment reports: WF6 justification for read across
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)
GLP compliance:
not specified
Type of assay:
mammalian cell gene mutation assay
Species / strain / cell type:
mouse lymphoma L5178Y cells
Metabolic activation:
with and without
Metabolic activation system:
Aroclor 1254-induced male Fischer 344 rat liver Sa
Test concentrations with justification for top dose:
Two laboratories performed the test. The highest dose of the study compound did not exceed 5 mg/mL.
Vehicle / solvent:
none
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
methylmethanesulfonate
Details on test system and experimental conditions:
Mouse lymphoma L5178Y cells were maintained at 37 °C as suspension cultures in Fischer's medium supplemented with 2 mM l-glutamine, 110 µg/mL sodium pyruvate, 0.05% pluronic F68, antibiotics and heat activated horse serum. To reduce the number of spontaneously occurring trifluorothymidine (TFT) resistant cells, subcultures were exposed once to medium containing THMG (thymidine, hypoxanthine, methotrexate, glycine) for one day, to THG for one day and to normal medium for 3 to 5 days.

Incubation with the study chemical continued for 4 hours, at which time the medium plus chemical was removed. The cells were resuspended in fresh medium and incubated for an additional 2 days to allow expression of the mutant phenotype. Cell density was monitored so that log phase growth was maintained. After the 48 hour expression period, 3 x 10(+6) cells were plated in medium and soft agar supplemented with trifluorothymidine for selection of TFT-resistant cells and 600 cells were plated in nonselective medium and soft agar to determine cloning efficiency. Plates were incubated at 37 °C in 5% carbon dioxide for 10 to 12 days.
Evaluation criteria:
All data was evaluated statistically for both trend and peak response. Both responses had to be significant (P<0.05) for a chemical to be considered positive and the absence of both trend and a peak response resulted in a negative call. Validation criteria are detailed in Myhr at al (1985). This assay is initially performed without S9; if a clearly positive response is not obtained, the experiment is repeated with induced S9.
Species / strain:
mouse lymphoma L5178Y cells
Metabolic activation:
with and without
Genotoxicity:
positive
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
Sodium fluoride was studied at two laboratories for induction of trifluorothymidine resistance in mouse L5178Y lymphoma cells. In the first laboratory, sodium fluoride was positive both with and without Aroclor 1254-induced male Fischer 344 rat liver S9, the effective doses, with and without S9, ranged from 300 to 600 µg/mL (Caspary et al, 1987). In the second laboratory, sodium fluoride was tested without S9 only, and test results were positive in the first trial at 62.5, 125, and 1,000 µg/mL and in the second trial at 800 and 900 µg/mL. The mutant colonies obtained after sodium fluoride treatment of L5178Y cells were primarily small colonies, suggesting that chromosomal abnormalities may be involved.
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'.

The table below shows the induction of trifluorothymidine resistance in mouse L5178Y cells by sodium fluoride;
Compound Concentration (µg/mL) Cloning Efficiency (%) Relative Total Growth (%) Tft Resistant Cells Mutant fraction
- S9   75.8 ±3.8 99.8 ±4.8 67.0 ±5.9 29.5 ±1.9
Trial 1
Distilled water
Sodium fluoride 200 85.5 ±18.5 81.5 ±8.5 80.5 ±13.5 32.0 ±2.0
300 85.3 ±4.7 72.0 ±5.2 133.3 ±22.3 52.7 ±9.4
400 78.7 ±0.9 41.0 ±4.0 107.7 ±4.9 45.7 ±1.9
500 75.0 ±3.8 16.7 ±2.7 125.0 ±16.7 55.3 ±4.8
600 79.5 ±3.5 10.0 ±1.0 196.0 ±3.0 83.0 ±5.0
800 Lethal      
Methyl methanesulfonate 5 66.7 ±2.4 70.7 ±5.2 489.0 ±43.7 244.3 ±13.2
- S9   105.7 ±9.1 100.0 ±9.1 77.0 ±2.5 24.3 ±1.9
Trial 2
Distilled water
Sodium fluoride 50 91.0 ±7.0 86.3 ±2.0 59.0 ±9.3 22.0 ±3.1
100 92.0 ±4.0 71.5 ±8.5 75.5 ±3.5 27.0 ±0
200 88.0 ±4.6 57.0 ±2.3 72.7 ±11.1 27.3 ±3.0
300 89.3 ±10.2 49.3 ±3.7 58.3 ±8.7 22.0 ±2.7
400 104.0 ±12.0 40.0 ±0.0 112.0 ±25.0 35.5 ±4.5
500 94.3 ±7.6 17.3 ±3.0 119.0 ±28.4 41.3 ±8.5
600 Lethal      
Methyl methanesulfonate 5 66.7 ±2.4 70.7 ±5.2 489.0 ±43.7 140 ±36.5
+ S9   107.5 ±1.3 100.0 ±6.8 83.8 ±6.9 25.8 ±2.1
Trial 3
Distilled water
Sodium fluoride 100 85 75 66 26
200 99.7 ±7.8 70.7 ±4.9 59.7 ±9.9 20.7 ±4.4
300 94.5 ±5.5 52.0 ±9.0 110.5 ±5.5 39.5 ±4.5
400 106.7 ±7.0 41.3 ±2.3 121 ±14.1 39.0 ±7.6
500 72.3 ±9.2 13.3 ±3.8 177.7 ±45.1 81.0 ±19.3
600 77.5 ±13.5 7.5 ±0.5 206.5 ±24.5 94.0 ±27.0
Methyl methanesulfonate 2.5 61.3 ±5.2 28.0 ±2.1 615.0 ±43.3 334.7 ±11.9
+ S9   82.3 ±3.0 100.0 ±9.3 81.5 ±8.7 33.0 ±2.4
Trial 3
Distilled water
Sodium fluoride 50 78.0 ±2.9 100.0 ±7.8 63.7 ±4.2 27.0 ±1.2
100 79.3 ±6.0 86.7 ±21.1 88.7 ±14.0 37.7 ±6.8
200 85.0 ±13.1 83.3 ±6.4 98.0 ±18.6 38.0 ±2.0
300 76.3 ±0.3 49.7 ±3.3 119.0 ±11.8 51.7 ±5.2
400 77.3 ±3.8 29.0 ±1.5 144.7 ±10.3 62.3 ±2.3
500 74.3 ±3.4 21.0 ±3.1 167.7 ±27.9 75.7 ±14.3
600 Lethal      
Methyl methanesulfonate 2.5 47.7 ±2.7 21.0 ±2.7 731.7 ±22.9 573.7 ±34.6
The table below shows the results obtained for the induction of trifluorothymidine resistance in mouse L5178Y/TK cells by sodium fluoride;
Compound Concentration (µg/mL) Cloning Efficiency (%) Relative Total Growth (%) Tft Resistant Cells Mutant fraction
- S9   58.8 ±3.0 100.0 ±10.3 101 ±14.0 58.0 ±9.7
Trial 1
Fischer’s medium without serum
Sodium fluoride 62.5 52.5 ±5.5 88.5 ±12.5 162.0 ±0.0 104.5 ±11.5
125 52.5 ±8.5 78.0 ±4.0 144.0 ±24.0 97.5 ±31.5
250 59.0 ±4.0 70.0 ±9.0 130.0 ±9.0 73.5 ±0.5
500 70.0 ±15.0 36.0 ±1.0 161.5 ±18.5 82.5 ±26.5
1000 40.0 ±4.0 8.0 ±3.0 155.5 ±13.5 134.0 ±25.0
Methyl methanesulfonate 15 16.5 ±1.5 13.0 ±2.0 172.0 ±3.0 342.5 ±24.5
- S9   90.5 ±5.72 100.0 ±5.3 138.3 ±12.8 51.0 ±4.1
Trial 2
Fischer's medium without serum
Sodium fluoride 500 82.0 ±3.0 33.0 ±0.0 145.0 ±20.0 58.5 ±5.5
600 87.0 ±10.0 28.0 ±3.0 148.5 ±0.5 58.0 ±7.0
700 90.5 ±3.5 25.0 ±0.0 177.0 ±25.0 66.0 ±12.0
800 78.5 ±0.5 20.0 ±1.0 215.5 ±22.5 91.5 ±9.5
900 78.0 ±2.0 13.0 ±1.0 445.0 ±22.0 195.5 ±3.5
1000 Lethal      
Methyl methanesulfonate 1552.0 ±4.0 52.0 ±4.0 35.0 ±1.0 77.0 ±14.0 49.0 ±5.0
Conclusions:
Interpretation of results (migrated information):
positive

In two laboratories, sodium fluoride was tested for induction of trifluorothymidine resistance in mouse L5178Y lymphoma cells; results were positive both with and without S9.
Executive summary:

Sodium fluoride was studied at two laboratories for induction of trifluorothymidine resistance in mouse L5178Y lymphoma cells. In the first laboratory, sodium fluoride was positive both with and without Aroclor 1254-induced male Fischer 344 rat liver S9, the effective doses, with and without S9, ranged from 300 to 600 µg/mL (Caspary et al, 1987). In the second laboratory, sodium fluoride was tested without S9 only, and test results were positive in the first trial at 62.5, 125, and 1,000 µg/mL and in the second trial at 800 and 900 µg/mL. The mutant colonies obtained after sodium fluoride treatment of L5178Y cells were primarily small colonies, suggesting that chromosomal abnormalities may be involved.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed (positive)

Additional information

Additional information from genetic toxicity in vitro:

Justification for selection of genetic toxicity endpoint
Study reviewed by the United States Governmental Organisation "NATIONALTOXICOLOGY PROGRAM" (NTP), U.S. DEPARTMENT OF HEALTH AND HUMANSERVICES, PublicHealthService, National Institutes of Health.Therefore it is consired as reasonably reliable. Study done according to OECD Guideline.

Justification for classification or non-classification