Zinc bis(N-ethyl-N-phenyldithiocarbamate)

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Experimental start date: 22 November 2017. Experimental completion date: 10 January 2018.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Zinc bis(N-ethyl-N-phenyldithiocarbamate)

EC Number:

238-677-1

EC Name:

Zinc bis(N-ethyl-N-phenyldithiocarbamate)

Cas Number:

14634-93-6

Molecular formula:

C18H20N2S4Zn

IUPAC Name:

zinc bis(N-ethyl-N-phenyldithiocarbamate)

Specific details on test material used for the study:

Identification: Vulkacit P extra N
Physical State / Appearance: White powder
Expiry Date: 04 December 2017
Storage Conditions: At room temperature
Stability in Solvent: No analytical determination of stability in solvent conducted, but all formulations were prepared freshly before treatment and used within two hours of preparation.
The dose selection was adjusted to purity.

Method

Target gene:

Histidine locus in S. typhimurium and tryptophan locus in E.coli.

Species / strain

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2

Metabolic activation:

with and without

Metabolic activation system:

Phenobarbital/β-naphthoflavone induced rat liver S9 were used as the metabolic activation system

Test concentrations with justification for top dose:

Pre-Experiment/Experiment I: 3; 10; 33; 100; 333; 1000; 2500; and 5000 µg/plate
The maximum concentration was 5000 μg/plate (the maximum recommended dose level).

Experiment II:
All strains without S9 mix: 10; 33; 100; 333; 1000; 2500 and 5000 µg/plate
All strains with S9 mix: 3, 10; 33; 100; 333; 1000; and 2500 µg/plate
Since toxic effects were observed in experiment I seven concentrations were tested in experiment II. 5000 µg/plate were chosen as maximal concentration for all strains without S9 mix, respectively 2500 µg/plate for all strains with S9 mix.

Experiment IIa:
Strains TA 1535, TA 1537,
TA 98, and WP2 uvrA with S9 mix: 10; 33; 100; 333; 1000; 2500; and 5000 µg/plate
Since no toxic effects were observed in experiment II in strains TA 1535, TA 1537, TA 98 and WP2 uvrA with S9 mix, this part of experiment II had to be repeated

Vehicle / solvent:

DMSO. The solvent was chosen because of its solubility properties and its relative nontoxicity to the bacteria

Controls

Controls 1

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Remarks:

10 µg/plate in strains TA 1535 and TA 100

Positive control substance:

sodium azide

Remarks:

Without metabolic activation

Controls 2

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Remarks:

10 µg/plate in strain TA 98, 50 µg/plate in strain TA 1537

Positive control substance:

other: 4-nitro-o-phenylene-diamine

Remarks:

Without metabolic activation

Controls 3

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Remarks:

2.0 µL/plate in strain WP2 uvrA

Positive control substance:

methylmethanesulfonate

Remarks:

Without metabolic activation

Controls 4

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Remarks:

2.5 µg/plate for TA 1535, TA 1537, TA 98, TA 100, 10.0 µg/plate in WP2 uvrA.

Positive control substance:

other: 2-aminoanthracene,

Remarks:

With metabolic activation

Details on test system and experimental conditions:

Pre-Experiment for Toxicity
To evaluate the toxicity of the test item a pre-experiment was performed with all strains used. Eight concentrations were tested for toxicity and mutation induction with each 3 plates. The experimental conditions in this pre-experiment were the same as described for the experiment I below (plate incorporation test).
Toxicity of the test item can be evident as a reduction in the number of spontaneous revertants or a clearing of the bacterial background lawn.
The pre-experiment is reported as main experiment I, since the following criteria were met:
Evaluable plates (>0 colonies) at five concentrations or more were used in all strains.

Experimental Performance
For each strain and dose level, including the controls, three plates were used.
Experiment I (Plate Incorporation)

The following materials were mixed in a test tube and poured onto the selective agar plates:
100 µL Test solution at each dose level (solvent or reference mutagen solution (positive control)),
500 µL S9 mix (for test with metabolic activation) or S9 mix substitution buffer (for test without metabolic activation),
100 µL Bacteria suspension (cf. test system, pre-culture of the strains),
2000 µL Overlay agar

Experiment II and IIa (Pre-Incubation)
In the pre-incubation assay 100 µL test solution (solvent or reference mutagen solution (positive control)), 500 µL S9 mix / S9 mix substitution buffer and 100 µL bacterial suspension were mixed in a test tube and incubated at 37°C for 60 minutes. After pre-incubation 2.0 mL overlay agar (45°C) was added to each tube.
The mixture was poured on minimal agar plates. After solidification the plates were incubated upside down for at least 48 hours at 37°C in the dark.
In parallel to each test a sterile control of the test item was performed and documented in the raw data. Therefore, 100 µL of the stock solution, 500 µl S9 mix / S9 mix substitution buffer were mixed with 2.0 mL overlay agar and poured on minimal agar plates.

Evaluation criteria:

A test item is considered as a mutagen if a biologically relevant increase in the number of revertants exceeding the threshold of twice (strains TA 98, TA 100, and WP2 uvrA) or thrice (strains TA 1535 and TA 1537) the colony count of the corresponding solvent control is observed.
A dose dependent increase is considered biologically relevant if the threshold is exceeded at more than one concentration.
An increase exceeding the threshold at only one concentration is judged as biologically relevant if reproduced in an independent second experiment.
A dose dependent increase in the number of revertant colonies below the threshold is regarded as an indication of a mutagenic potential if reproduced in an independent second experiment. However, whenever the colony counts remain within the historical range of negative and solvent controls such an increase is not considered biologically relevant.

Results and discussion

Test results

Test results 1

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 2

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 3

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 4

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 5

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

The test item Vulkacit P Extra N was assessed for its potential to induce gene mutations according to the plate incorporation test (experiment I) and the pre-incubation test (experiment II and IIa) using Salmonella typhimurium strains TA 1535, TA 1537, TA 98, TA 100, and the Escherichia coli strain WP2 uvrA.
The assay was performed in two independent experiments both with and without liver microsomal activation. Each concentration and the controls were tested in triplicate. The test item was tested at the following concentrations:
Pre-Experiment/Experiment I: 3; 10; 33; 100; 333; 1000; 2500; and 5000 µg/plate
Experiment II:
All strains without S9 mix: 10; 33; 100; 333; 1000; 2500 and 5000 µg/plate
All strains with S9 mix: 3, 10; 33; 100; 333; 1000; and 2500 µg/plate
Experiment IIa:
Strains TA 1535, TA 1537,
TA 98, and WP2 uvrA with S9 mix: 10; 33; 100; 333; 1000; 2500; and 5000 µg/plate
The test item precipitated in the overlay agar in the test tubes from 333 to 5000 µg/plate in all experiments. Precipitation of the test item in the overlay agar on the incubated agar plates was observed from 1000 to 5000 µg/plate, respectively the highest investigated dose in all experiments. The undissolved particles had no influence on the data recording.

No substantial increase in revertant colony numbers of any of the five tester strains was observed following treatment with Vulkacit P Extra N at any concentration level, neither in the presence nor absence of metabolic activation (S9 mix). There was also no tendency of higher mutation rates with increasing concentrations in the range below the generally acknowledged border of biological relevance.
Appropriate reference mutagens were used as positive controls. They showed a distinct in-crease in induced revertant colonies.

Any other information on results incl. tables

Results

The plates incubated with the test item showed reduced background growth at the following concentrations (µg/plate):

Strain	Experiment I		Experiment II		Experiment IIa
	without S9 mix	with S9 mix	without S9 mix	with S9 mix	with S9 mix
TA 1535	/	/	/	/	/
TA 1537	/	/	/	333 – 2500	1000 – 5000
TA 98	/	/	/	1000 – 2500	1000 – 5000
TA 100	/	/	/	333 – 2500	n.p.
WP2 uvrA	/	/	/	/	1000 – 5000

/ = normal background growth; n.p. = not performed

Toxic effects, evident as a reduction in the number of revertants (below the induction factor of 0.5), were observed at the following concentrations (µg/plate):

Strain	Experiment I		Experiment II		Experiment IIa
	without S9 mix	with S9 mix	without S9 mix	with S9 mix	with S9 mix
TA 1535	/	5000	/	/	2500 – 5000
TA 1537	5000	5000	5000	/	2500 – 5000
TA 98	5000	2500 – 5000	2500 – 5000	/	1000 – 5000
TA 100	5000	1000 – 5000	5000	333 – 2500	n.p.
WP2 uvrA	5000	2500 – 5000	5000	/	5000

/ = no toxic effects, evident as a reduction in the number of revertants (below the induction factor of 0.5)

n.p.: not performed

Summary of Experiment 1

Metabolic Activation	Test Group	Dose Level (per plate)		Revertant Colony Counts (Mean ±SD)
				TA 1535	TA 1537	TA 98	TA 100	WP2 uvrA
Without Activation	DMSO, dried			9 ± 2	10 ± 3	25 ± 6	185 ± 15	29 ± 3
	Untreated			13 ± 4	9 ± 4	33 ± 4	187 ± 12	31 ± 9
	Vulkacit P	3 µg		8 ± 3	9 ± 4	22 ± 6	201 ± 4	29 ± 6
	Extra N	10 µg		9 ± 1	11 ± 4	26 ± 6	213 ± 10	27 ± 3
		33 µg		10 ± 3	10 ± 6	27 ± 6	202 ± 16	40 ± 5
		100 µg		12 ± 3	11 ± 3	31 ± 5	200 ± 17	31 ± 10
		333 µg		11 ± 0	10 ± 5	32 ± 6	167 ± 14	27 ± 9
		1000 µg		13 ± 2^P	12 ± 2^P	25 ± 3^P	153 ± 16^P	27 ± 8^P
		2500 µg		7 ± 2^P M	6 ± 1^P M	13 ± 2^P M	108 ± 15^P	16 ± 1^P M
		5000 µg		5 ± 1^P M	3 ± 1^P M	3 ± 1^P M	40 ± 3^P M	6 ± 2^P M
	NaN3	10 µg		1305 ± 27			2165 ± 89
	4-NOPD	10 µg				329 ± 33
	4-NOPD	50 µg			122 ± 5
	MMS	2.0 µL						1005 ± 42
With Activation	DMSO, dried			14 ± 2	12 ± 4	35 ± 12	139 ± 15	45 ± 7
	Untreated			10 ± 2	19 ± 2	37 ± 7	195 ± 12	45 ± 4
	Vulkacit P	3 µg		10 ± 3	17 ± 3	38 ± 5	131 ± 7	39 ± 9
	Extra N	10 µg		12 ± 3	13 ± 2	35 ± 9	120 ± 16	45 ± 7
		33 µg		11 ± 5	19 ± 2	38 ± 2	134 ± 12	50 ± 9
		100 µg		11 ± 4	12 ± 1	33 ± 4	129 ± 13	46 ± 12
		333 µg		13 ± 2	21 ± 2	30 ± 2	96 ± 29	39 ± 8
		1000 µg		12 ± 1^P	18 ± 2^P	26 ± 1^P	60 ± 3^P	38 ± 11^P
		2500 µg		9 ± 3^P	8 ± 2^P M	13 ± 4^P M	46 ± 4^P M	18 ± 1^P M
		5000 µg		5 ± 2^P M	3 ± 1^P M	6 ± 2^P M	29 ± 2^P M	10 ± 1^P M
	2-AA	2.5 µg		469 ± 13	134 ± 21	4692 ± 474	3713 ± 289
	2-AA	10.0 µg						425 ± 13

Summary of Experiment II

Metabolic Activation	Test Group	Dose Level (per plate)	Revertant Colony Counts (Mean ±SD)
			TA 1535	TA 1537	TA 98	TA 100	WP2 uvrA
Without Activation	DMSO, dried		10 ± 1	11 ± 1	26 ± 0	161 ± 10	33 ± 4
	Untreated		9 ± 2	15 ± 5	25 ± 3	198 ± 38	33 ± 10
	Vulkacit P	10 µg	8 ± 3	9 ± 2	29 ± 7	176 ± 21	33 ± 8
	Extra N	33 µg	9 ± 3	10 ± 3	21 ± 4	146 ± 24	33 ± 6
		100 µg	11 ± 2	10 ± 3	17 ± 4	187 ± 19	40 ± 6
		333 µg	9 ± 0	9 ± 2	26 ± 2	140 ± 28	31 ± 9
		1000 µg	10 ± 3^P	10 ± 4^P	28 ± 5^P	150 ± 12^P	30 ± 3^P
		2500 µg	6 ± 1^P M	6 ± 1^P M	11 ± 2^P M	89 ± 10^P M	16 ± 2^P M
		5000 µg	6 ± 1^P M	2 ± 2^P M	2 ± 2^P M	30 ± 5^P M	6 ± 1^P M
	NaN3	10 µg	1149 ± 128			1762 ± 259
	4-NOPD	10 µg			354 ± 16
	4-NOPD	50 µg		190 ± 9
	MMS	2.0 µL					859 ± 74
With Activation	DMSO, dried		12 ± 3	12 ± 4	30 ± 2	142 ± 21	37 ± 10
	Untreated		13 ± 2	14 ± 2	40 ± 7	202 ± 3	43 ± 13
	Vulkacit P	3 µg	11 ± 3	14 ± 2	34 ± 6	134 ± 12	45 ± 4
	Extra N	10 µg	11 ± 1	13 ± 2	30 ± 7	102 ± 15	47 ± 12
		33 µg	9 ± 3	11 ± 4	24 ± 3	94 ± 12	41 ± 5
		100 µg	9 ± 3	15 ± 4	43 ± 9	91 ± 3	38 ± 9
		333 µg	11 ± 5	14 ± 7^R	29 ± 9	40 ± 12^R	34 ± 5
		1000 µg	8 ± 3^P	7 ± 1^P M R	24 ± 3^P R	31 ± 9^P R	33 ± 6^P
		2500 µg	7 ± 1^P M	7 ± 2^P M R	16 ± 2^P M R	28 ± 3^P M R	22 ± 3^P M
	2-AA	2.5 µg	476 ± 11	97 ± 8	3413 ± 629	2726 ± 213
	2-AA	10.0 µg					546 ± 40

Summary of Experiment IIA

Metabolic Activation	Test Group	Dose Level (per plate)		Revertant Colony Counts (Mean ±SD)
				TA 1535	TA 1537	TA 98	WP2 uvrA
With Activation	DMSO, dried			11 ± 1	11 ± 1	31 ± 10	35 ± 12
	Untreated			8 ± 2	22 ± 9	36 ± 9	40 ± 5
	Vulkacit P	10 µg		9 ± 3	12 ± 3	35 ± 7	44 ± 4
	Extra N	33 µg		12 ± 2	11 ± 5	38 ± 6	34 ± 11
		100 µg		15 ± 5	13 ± 4	30 ± 3	33 ± 12
		333 µg		11 ± 1	13 ± 3	27 ± 1	35 ± 5
		1000 µg		8 ± 2^P	11 ± 3^R P	14 ± 5^R M P	33 ± 5^P R
		2500 µg		5 ± 2^P M	4 ± 2^P M R	10 ± 3^P M R	22 ± 5^P M R
		5000 µg		1 ± 1^P M	2 ± 1^P M R	6 ± 1^P M R	11 ± 3^P M R
	2-AA	2.5 µg		451 ± 33	122 ± 17	3612 ± 1049
	2-AA	10.0 µg					334 ± 63

Key to Positive Controls		Key to Plate Postfix Codes
NaN3 2-AA 4-NOPD MMS	sodium azide 2-aminoanthracene 4-nitro-o-phenylene-diamine methyl methane sulfonate	P M R	Precipitate Manual count Reduced background growth

Applicant's summary and conclusion

Conclusions:

In conclusion, it can be stated that during the described mutagenicity test and under the experimental conditions reported, the test item, Vulkacit P Extra N, did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used.

Executive summary:

This study was performed to investigate the potential of Vulkacit P Extra N to induce gene mutations according to the plate incorporation test (experiment I) and the pre-incubation test (experiment II and IIa) using the Salmonella typhimurium strains TA 1535, TA 1537, TA 98, TA 100, and the Escherichia coli strain WP2 uvrA.

The assay was performed in three independent experiments with and without liver microsomal activation. Each concentration, including the controls, was tested in triplicate. The test item was tested at the following concentrations:

Pre-Experiment/Experiment I:         3; 10; 33; 100; 333; 1000; 2500; and 5000 µg/plate

Experiment II:

All strains without S9 mix:               10; 33; 100; 333; 1000; 2500 and 5000 µg/plate

All strains with S9 mix:                    3, 10; 33; 100; 333; 1000; and 2500 µg/plate

Experiment IIa:

Strains TA 1535, TA 1537,
TA 98, and WP2 uvrA with S9 mix:  10; 33; 100; 333; 1000; 2500; and 5000 µg/plate

The test item precipitated in the overlay agar in the test tubes from 333 to 5000 µg/plate in all experiments. Precipitation of the test item in the overlay agar on the incubated agar plates was observed from 1000 to 5000 µg/plate, respectively the highest investigated dose in all experiments. The undissolved particles had no influence on the data recording.

In experiment I the plates incubated with the test item showed normal background growth up to 5000 µg/plate with and without S9 mix in all strains used. In experiment II and IIa reduced background growth was observed in all strains used with S9 mix except of strain TA 1535.

Toxic effects, evident as a reduction in the number of revertants (below the indication factor of 0.5), occurred in all strains.

No substantial increase in revertant colony numbers of any of the fivetester strains was observed following treatment with Vulkacit P Extra N at any dose level, neither in the presence nor absence of metabolic activation (S9 mix). There was also no tendency of higher mutation rates with increasing concentrations in the range below the generally acknowledged border of biological relevance.

Appropriate reference mutagens were used as positive controls and showed a distinct increase of induced revertant colonies.

Conclusion

In conclusion, it can be stated that during the described mutagenicity test and under the experimental conditions reported, the test item did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used.

Therefore, Vulkacit P Extra N is considered to be non-mutagenic in this Salmonella typhimurium and Escherichia coli reverse mutation assay.