Potassium thiosulphate

Specific investigations: other studies

Administrative data

Endpoint:

specific investigations: other studies

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well-documented short publication. Supplementary data with respect to the mechanism of cell transformation.

Data source

Reference

Reference Type:

publication

Title:

Transformation of Syrian hamster embryo cells by sodium bisulfite.

Author:

DiPaolo, J.A.; et al.

Year:

1981

Bibliographic source:

Cancer Letters, 12, 203- 208

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Transformation of Syrian hamster embryo cells (HEC) by bisulfite and after treatment with UV irradiation. Two-day-old secondary hamster cultures
were treated 24 h after plating for 15 min with varying concentrations of sodium bisulfite in PBS (0, 1, 5, 10, or 20 mM). With this procedure, all bisulfite treatment was at neutral pH. After treatment incubation was for 6 more days before determination of cell survival of HEC and transformation.

GLP compliance:

no

Type of method:

in vitro

Endpoint addressed:

carcinogenicity

Test material

Test material information

Constituent 1

Reference substance name:

Sodium hydrogensulfite

EC Number:

231-548-0

EC Name:

Sodium hydrogensulfite

Cas Number:

7631-90-5

Molecular formula:

NaHSO3

IUPAC Name:

sodium hydrogensulfite

Details on test material:

- Name of test material (as cited in study report): sodium bisulfite
- Molecular formula (if other than submission substance): NaHSO3
- Molecular weight (if other than submission substance): 104.06 g/mol
- Physical state: solid
- Analytical purity: Fisher certified mreagent sodium bisulfite was purchased from Fisher Scientific Co., Fairlawn, NJ

Test animals

Details on test animals or test system and environmental conditions:

not applicable

Administration / exposure

Details on exposure:

- Two-day-old secondary hamster cultures were treated 24 h after plating for 15 min with varying concentrations of sodium bisulfite in PBS (0, 1, 5, 10, or 20 mM).
- With this procedure, all bisulfite treatment was at neutral pH.
- After treatment incubation was for 6 more days before determination of cell survival of HEC and transformation.

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
1 mM K2S2O5
Basis:
nominal conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
5 mM K2S2O5
Basis:
nominal conc.

Doses / concentrations 3

Remarks:

Doses / Concentrations:
10 mM K2S2O5
Basis:
nominal conc.

Doses / concentrations 4

Remarks:

Doses / Concentrations:
20 mM K2S2O5
Basis:
nominal conc.

No. of animals per sex per dose:

not applicable

Details on study design:

- Fresh HEC cells from foetuses 13-14 days in gestation were used.
- Primary and subsequent passage cells were grown as monolayers in Petri dishes in complete medium at 37 °C in 11 % CO2 humified atmosphere.
- The medium consisted of Dulbecco’s modification of Eagle’Sminimal essential medium with 10 % foetal bovine serum supplemented with hypoxanthine and thymidine.
- In all experiments, 2-day old hamster cultures obtained by seeding 2.5 x 10E6 cell/100 mm-dish, were used.
- Fort he quantitative assay, 300 cells were co-cultivated with 6 x 10E4 X-irradiation killed HEC in 60 mm dishes.
- Cells cultures were treated 24 h after being seeded by first removing the medium and incubation 15 min with varying concentrations of sodium bisulfite in PBS. With this procedure, all bisulfite treatment was at neutral pH.
- After treatment, the bisulfite solution was removed, complete medium with 15 %foetal bovine serum was added and incubation was continued for an additional 6 days prior tot he staining of cells.
- Transformation and cell survival of HEC were determined in the same dishes. Colony morphology was determined with a microscope at x10 – x50. The non-transformed colonies had a regularly oriented arrangement of cells whereas the transformed ones exhibited a random criss-cross piling up of cells not observed in untreated controls.
- Transformation was calculated both per dish and relative to the number of colonies surviving. The cloning efficiency (CE) was determined by dividing the average number of colonies by the number of cells seeded per plate, and multiplying with 100.
- Cells were UV irradiated. For UV treatment the medium was removed and the cells were irradiated through a Permanox top and covered with PBS for 15 min.
- Fort he UV and bisulfite combinations the cells were treated with bisulfite in 1 mL PBS before and after irradiation. After final treatment, the PBS was replaced with complete medium.

Results and discussion

Details on results:

- Concentrations of sodium bisulfite between 1 to 20 mM that caused minimal toxicity caused a dose-dependent increase in the transformation of Syrian hamster embryo cells.
- Exposure of the cells to bisulfite (up to 10 mM) either before or after UV irradiation with 3 J/m2 did not result in an increased transformation frequency.
- The results suggest that bisulfite transformation of HEC may not occur by a mechanism involving mutation.

Applicant's summary and conclusion

Conclusions:

From this study it may be suggested that the transformation of HEC by bisulfite did not occur by a mechanism involving mutation.