Zinc bis(diethyldithiocarbamate)

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in mammalian cells

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1998

Report date:

1998

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)

Version / remarks:

UKEMS guidelines

Deviations:

yes

Remarks:

only large mutant colonies (diameter > 0.5 mm) were scored

GLP compliance:

not specified

Type of assay:

mammalian cell gene mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Zinc bis(diethyldithiocarbamate)

EC Number:

238-270-9

EC Name:

Zinc bis(diethyldithiocarbamate)

Cas Number:

14324-55-1

Molecular formula:

C10H20N2S4Zn

IUPAC Name:

zinc bis(diethyldithiocarbamate)

Details on test material:

- Name of test material (as cited in study report): ZDEC
- Physical state: fine (aggregative) white powder
- Purity: at least 98%
- Impurities (identity and concentrations): ZDBC (1000 ppm) and TETD (56 ppm)
- Lot/batch No.: 2036 92001

Method

Target gene:

Thymidine kinase

Species / strain

Species / strain / cell type:

mouse lymphoma L5178Y cells

Additional strain / cell type characteristics:

other: cells heterozygous at the thymidine kinase gene locus (TK +/-)

Metabolic activation:

with and without

Metabolic activation system:

S-9 mix

Test concentrations with justification for top dose:

0.0025, 0.005, 0.01, 0.025 and 0.05 µg/ml without metabolic activation.
0.025, 0.05, 0.1, 0.2, 0.4 and 0.6 µg/ml with metabolic activation.

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO

Controls

Untreated negative controls:

not specified

Negative solvent / vehicle controls:

yes

True negative controls:

not specified

Positive controls:

yes

Positive control substance:

7,12-dimethylbenzanthracene

ethylmethanesulphonate

other: ZDMC

Details on test system and experimental conditions:

METHOD OF APPLICATION: soft agar cloning technique

Results and discussion

Test results

Key result

Species / strain:

mouse lymphoma L5178Y cells

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not specified

Positive controls validity:

valid

Additional information on results:

RANGE-FINDING/SCREENING STUDIES:
ZDEC proved highly cytotoxic: following preliminary toxicity tests, L5178Y cells were treated at five concentrations between 0.0025 and 0.05 µg/ml in the absence of S-9 mix and 0.025-0.6 µg/ml in its presence.

Any other information on results incl. tables

In the first mutation experiment, total growth (% of control value: calculated as % suspension growth x % cloning growth /100) in test cultures ranged from 113 to 4.4% without S-9 mix and 119 to 59% in its presence. In the second experiment, these ranges were respectively 102-8% and 103-9%. Even after exposure at clearly cytotoxic concentrations of ZDEC, there were no significant increases in either mutant colony numbers or calculated mutant frequencies. It was concluded that ZDEC gave negative results in this assay. These results are summarized in Table 1.

In reference control cultures treated with ZDMC, there was evident cytotoxicity: total growth was 7% or 2% of control values at 0.5 µg/ml without S-9 mix, 15% of control at 1 µg/ml with S-9 mix (Experiment 2 only: in Experiment 1, ZDMC was tested at 0.7 µg/ml and total growth was reduced to only 72%). No meaningful increases in mutant colony numbers or mutation frequencies were seen in non-activated ZDMC test cultures, but with S-9 mix an apparent effect was seen in Experiment 1 only: after exposure at 0.7 µg/ml, mutant colony numbers showed a consistent (> twofold) increase over solvent controls, leading to a doubling of the calculated mutation frequency. Exposure to ZDMC at the slightly higher (and more cytotoxic) concentration of 1 µg/ml in Experiment 2 (again with S-9 mix) showed a doubling of mutant colony numbers and 1.5-fold increase in calculated mutation frequency in one of the two replicate cultures, while the duplicate culture showed no such increases. Owing to the known variation of spontaneous mutation frequency in the L5178Y TK + /- assay system, a larger (e.g. at least threefold) and clearly reproducible increase in mutation frequency is required before a positive result is concluded. It was therefore concluded from these test data that ZDMC showed no evidence of mutagenic activity without S-9 mix, and also gave a negative (or, at most, equivocal) result in the presence of the S-9 mix activating system.

Table 1: Mean total growth (TG), mutantcolony numbers(MC), mutation frequencies (MF) andinduced mutation frequencies(IMF) recorded in L5178Y TK + /- mutation assays with ZDEC

		Experiment 1				Experiment 2
Treatment (µg/ml)	S-9 mix	TG (%)	MC (/plate)	MF (x10^-5)	IMF (x10^-5)	TG (%)	MC (/plate)	MF (x10^-5)	IMF (x10^-5)
DMSO (0)	-	100	62	9.1	0	100	23	4.4	0
ZDEC, 0.0025	-	113	63	9.8	+0.7	80	21	5.0	+0.6
ZDEC, 0.005	-	69	42	7.4	-1.7	99	16	3.9	-0.5
ZDEC, 0.01	-	6	42	10.9	+1.8	102	28	4.4	0
ZDEC, 0.025	-	3	36	9.4	+0.3	25	39	6.9	+2.5
ZDEC, 0.05	-	4	45	10	+0.9	8	31	7.2	+2.8
EMS*, 500	-	35	236	51.2	+42.1	35	129	52.1	+47.7
ZDMC, 0.5	-	7	42	10.2	+1.1	2	21	7.1	+3.0
DMSO (0)	+	100	42	7.0	0	100	24	4.4	0
ZDEC, 0.025	+	99	65	8.8	+1.8	NT	30	NT	NT
ZDEC, 0.05	+	111	87	12.0	+5.0	103	39	4.5	+0.1
ZDEC, 0.1	+	119	89	11.6	+4.6	88	55	6.5	+2.1
ZDEC, 0.2	+	94	42	7.3	+0.3	53	48	8.0	+3.6
ZDEC, 0.4	+	59	51	7.6	+0.6	46	32	8.9	+4.5
ZDEC, 0.6	+	NT	NT	NT	NT	9	51	8.2	+3.8
DMBA*, 5	+	7	97	31.7	+24.7	3	44	24.3	+19.9
DMBA*, 5	-	119	108	14.4	+7.4	105	44	5.7	+1.3
ZDMC, 0.7	+	72	107	15.1	+8.1	NT	NT	NT	NT
ZDMC, 1.0	+	NT	NT	NT	NT	15	31	5.1	+0.7

NT = not tested

All values are rounded to the nearest significant figure shown.

*Positive controls:EMS= ethyl methanesulfonate; DMBA = 7,12-dimethylbenzanthracene