Cobalt trihydroxide

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Remarks:

Type of genotoxicity: gene mutation

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: Methodical and reporting deficiencies. Supportive data only.

Cross-reference

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

publication

Title:

Conditions for detecting the mutagenicity of divalent metals in Salmonella typhimurium

Author:

Pagano, D.A.; Zeiger, E.

Year:

1992

Bibliographic source:

Environ. Mol. Mutagen. 19, 139-146

Materials and methods

Principles of method if other than guideline:

Reverse mutation testing in S. typhimurium strain TA97 without metabolic activation in four dose steppings up to 500µM.

GLP compliance:

not specified

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Cobalt chloride

IUPAC Name:

Cobalt chloride

Details on test material:

- Name of test material (as cited in study report): Cobalt chloride (Co++) from Sigma Chemical Co., St. Louis, MO.- Physical state: solidno further details reported

Method

Target gene:

his

Species / strain

Species / strain / cell type:

S. typhimurium TA 97

Additional strain / cell type characteristics:

not specified

Metabolic activation:

without

Test concentrations with justification for top dose:

doses: 0.0, 62.5, 125, 250, 500µM

Vehicle / solvent:

- different aqueous solvents used: Vogel-Bonner medium (VB): MgSO4, NaNH4HPO4, K2HPO4 and citrate; individual VB salt components were made 50x in distilled, deionized water (ddH2O) and diluted to 1x on the day of testing. Citrate was adjusted to pH 4.5 with 5N NaOH.
- test item were dissolved and diluted in ddH20 on the day of testing.
- no further significant details stated

Controls

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

no

Positive control substance:

no

Details on test system and experimental conditions:

Examining alterations in the Salmonella preincuabtion protocol that would enhance detection of metals as mutagens. Testing was done in the presence of individual components of the Vogel-Bonner agar used in top and bottom agars.

METHOD OF APPLICATION:
Media and Reagents
Petri dishes contained 30 ml of minimal medium in 1.5% Bacto-Difco agar supplemented with 0.5% glucose and 12.5mM d-biotin. Top agar was prepared by adding 10.0 ml of a 0.5 mM L-histidine-0.5mM d-biotin solution 2.5 ml of a 20% glucose solution and 2.0 ml of a 50x concentration of Vogel-Bonner salts, to 100.0 ml of 0.6% agar.

Procedure
Salmonella Strain TA97 (from Prof. B.N. Ames, Berkeley, CA) was grown overnight in Oxoid No. 2 broth to a density of approx. 1x10E9 cells/ml.
Preincubation mutagenesis tests were done in triplicate. Individual stock components of Vogel-Bonner salts were diluted such that 50 μl gave the final conc. found in agar. The preincubation mix contained 500μl water , 50μl metal, 100 μl cells, 50μl Vogel-Bonner component, added in that order.
Tubes were incubated for 30 min. at 37°C. without shaking. Two ml of top agar were added to each tube, the content mixed, and plated on minimal bottom agar plates. His+ colonies were scored after 44 to 48 hours incubation at 37°C.
Repeat experiments were done on different days.

DETERMINATION OF CYTOTOXICITY
not reported

Evaluation criteria:

A positive response was defined as a reproducible, dose-related increase in revertants over the solvent control value. There was no requirement for a doubling response, or any specific fold or numerical increase.

Statistics:

- No formal statistical procedures were applied to the data.

Results and discussion

Test results

Species / strain:

S. typhimurium TA 97

Metabolic activation:

without

Genotoxicity:

positive

Remarks:

at 62.5µM and above

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

not specified

Untreated negative controls validity:

not specified

Positive controls validity:

not specified

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Any other information on results incl. tables

Table: The effect of components of Vogel-Bonner medium on the mutagenicity in Salmonella strain TA97

 

		Additions to preincubation mix
Metal	μM	None	MgSO4	NH4HPO4	K2HPO4	Citrate
Co++	0.0	110±13	117±15	124±14	113±2	105±24
	62.5	268±26	134±20	169±10	100±17	127±11
	125	438±33	138±20	331±54	125±8	97±15
	250	503±48	360±30	577±15	305±35	113±11
	500	517±72	418±46	379±47	468±17	104±10

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information):
positive

Some methodical and reporting deficiencies. Supportive data only.