Butan-2-one O,O',O''-(vinylsilylidyne)trioxime

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From June 17 to July 2, 1986

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

A standard NTP (National Toxicology Program) protocol.

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Unnamed

Year:

1986

Reference 2

Reference Type:

publication

Title:

Unnamed

Year:

1999

Materials and methods

Test guideline

Qualifier:

equivalent or similar to

Guideline:

OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)

GLP compliance:

not specified

Type of assay:

other: in vitro mammalian chromosome aberration test

Test material

Reference

Name:

Unnamed

Type:

Constituent

Details on test material:

- Name of test material (as cited in study report): Methyl ethyl ketoxime

Method

Species / strain

Species / strain / cell type:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Metabolic activation system:

S9 mix (Aroclor 1254-induced male Sprague-Dawley rat liver S9)

Test concentrations with justification for top dose:

Without metabolic activation: 1873, 2497, 3727, 5000 µg/mL
With metabolic activation: 2513, 3750, 5000 µg/mL

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: Dimethyl Sulfoxide

Controls

Controls 1

Negative solvent / vehicle controls:

yes

Remarks:

(Dimethyl Sulfoxide)

Controls 2

Positive controls:

yes

Positive control substance:

mitomycin C

Controls 3

Positive controls:

yes

Positive control substance:

cyclophosphamide

Details on test system and experimental conditions:

METHOD OF APPLICATION: In the test without S9, cells were incubated in McCoy’s 5A medium with methyl ethyl ketoxime for 18 hours; Colcemid was added and incubation continued for 2 hours. The cells were then harvested by mitotic shake-off, fixed, and stained with Giemsa. For the test with S9, cells were treated with methyl ethyl ketoxime and S9 for 2 hours, after which the treatment medium was removed and the cells incubated for 10 hours in fresh medium, with Colcemid present for the final 2 hours. Cells were harvested in the same manner as for the treatment without S9. The harvest time for the test was based on the cell cycle information obtained in the SCE test; because some cytotoxicity and cell cycle delay were anticipated in the absence of S9, the incubation period was extended. Cells were selected for scoring on the basis of good morphology and completeness of karyotype (21 ± 2 chromosomes). All slides were scored blind and those from a single test were read by the same person. Up to 200 first-division metaphase cells were scored at each dose level. Classes of aberrations included simple (breaks and terminal deletions), complex (rearrangements and translocations), and other (pulverized cells, despiralized chromosomes, and cells containing 10 or more aberrations).

Evaluation criteria:

Chromosomal aberration data are presented as percentages of cells with aberrations. To arrive at a statistical call for a trial, analyses were conducted on both the dose response curve and individual dose points. For a single trial, a statistically significant (P>=0.05) difference for one dose point and a significant trend (P>=0.003) were considered weak evidence for a positive response; significant differences for two or more doses indicated the trial was positive. A positive trend test, in the absence of a statistically significant increase at any one dose resulted in an equivocal call. Ultimately, the trial calls were based on a consideration of the statistical analyses as well as the biological information available to the reviewers.

Statistics:

Significance of percent cells with aberrations tested by the linear regression trend test versus log of the dose. Analyses were conducted on both the dose response curve and individual dose points

Results and discussion

Test results

Key result

Species / strain:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Genotoxicity:

negative

Remarks:

(up to 5000 µg/mL)

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

valid

Positive controls validity:

valid

Any other information on results incl. tables

Results of Chromosome Aberration test:

Trial #:1   Activation: No Activation   Date: 07/02/1986   Harvest Time: 20.0 hrs   Trial Call: Negative
		Dose (µg/mL)	Total Cells Examined	Total Aberrations			Complex Aberrations			Simple Aberrations			Other Abs.
				No. of	Abs	% Cells	No. of	Abs	% Cells	No. of	Abs	% Cells	No. of	Abs	% Cells
				Abs.	Per	With	Abs.	Per	With	Abs.	Per	With	Abs.	Per	With
					Cell	Abs.		Cell	Abs.		Cell	Abs.		Cell	Abs.
Vehicle Control	Negative (Not Specified)		200	2	0.010	1.0	1	0.005	0.5	1	0.005	0.5	0	0.000	0.0
Vehicle Control	Dimethyl Sulfoxide		200	5	0.025	2.5	1	0.005	0.5	4	0.020	2.0	0	0.000	0.0
Test Chemical	Methyl ethyl ketoxime	1873	200	2	0.010	1.0	0	0.000	0.0	2	0.010	1.0	0	0.000	0.0
		2497	200	5	0.025	2.5	0	0.000	0.0	5	0.025	2.5	0	0.000	0.0
		3727	200	1	0.005	0.5	1	0.005	0.5	0	0.000	0.0	0	0.000	0.0
		5000	0	0	0.000	0.0	0	0.000	0.0	0	0.000	0.0	0	0.000	0.0
Positive Control	Mitomycin-C	0.05	200	31	0.155	12.5	16	0.080	7.5	15	0.075	6.0	0	0.000	0.0
		0.08	25	9	0.360	36.0	4	0.160	16.0	5	0.200	20.0	0	0.000	0.0
	Trend			-1.211			0.069			-1.345
	Probability			0.887			0.472			0.911

 

Trial #:2   Activation: No Activation   Date: 06/17/1986   Harvest Time: 20.0 hrs   Trial Call: Test Failure
		Dose (µg/mL)	Total Cells Examined	Total Aberrations			Complex Aberrations			Simple Aberrations			Other Abs.
				No. of	Abs	% Cells	No. of	Abs	% Cells	No. of	Abs	% Cells	No. of	Abs	% Cells
				Abs.	Per	With	Abs.	Per	With	Abs.	Per	With	Abs.	Per	With
					Cell	Abs.		Cell	Abs.		Cell	Abs.		Cell	Abs.
Vehicle Control	Dimethyl Sulfoxide		200	5	0.025	2.0	0	0.000	0.0	5	0.025	2.0	0	0.000	0.0
Test Chemical	Methyl ethyl ketoxime	2500	200	7	0.035	3.5	0	0.000	0.0	7	0.035	3.5	0	0.000	0.0
Positive Control	Mitomycin-C	0.08	25	11	0.440	28.0	4	0.160	12.0	7	0.280	20.0	0	0.000	0.0
	Trend			0.000			0.000			0.000
	Probability			0.000			0.000			0.000

 

Trial #:1   Activation: Induced Rat Liver S9   Date: 06/17/1986   Harvest Time: 12.0 hrs   Trial Call: Negative
		Dose (µg/mL)	Total Cells Examined	Total Aberrations			Complex Aberrations			Simple Aberrations			Other Abs.
				No. of	Abs	% Cells	No. of	Abs	% Cells	No. of	Abs	% Cells	No. of	Abs	% Cells
				Abs.	Per	With	Abs.	Per	With	Abs.	Per	With	Abs.	Per	With
					Cell	Abs.		Cell	Abs.		Cell	Abs.		Cell	Abs.
Vehicle Control	Negative (Not Specified)		200	6	0.030	2.5	2	0.010	1.0	4	0.020	2.0	0	0.000	0.0
Vehicle Control	Dimethyl Sulfoxide		200	6	0.030	2.5	2	0.010	1.0	4	0.020	2.0	0	0.000	0.0
Test Chemical	Methyl ethyl ketoxime	2513	200	6	0.030	2.5	2	0.010	1.0	4	0.020	2.0	0	0.000	0.0
		3750	200	8	0.040	3.0	4	0.020	2.0	4	0.020	1.5	0	0.000	0.0
		5000	200	4	0.020	2.0	1	0.005	0.5	3	0.015	1.5	0	0.000	0.0
Positive Control	Cyclophosphamide	7.5	200	32	0.160	11.5	13	0.065	4.0	19	0.095	7.5	0	0.000	0.0
		37.5	25	13	0.520	44.0	4	0.160	16.0	9	0.360	32.0	0	0.000	0.0
	Trend			-0.166			-0.063			-0.493
	Probability			0.566			0.525			0.689

Applicant's summary and conclusion

Conclusions:

No increase in chromosomal aberrations was observed in cultured Chinese hamster ovary cells treated with up to 5000 μg/mL methyl ethyl ketoxime, with or without S9

Executive summary:

A cytogenetic Chromosome aberration tests with cultured Chinese hamster ovary cells was performed on methyl ethyl ketoxime according to NTP's standard protocol (test method similar to OECD Guideline 473). Chinese hamster ovary cells were exposed to 2513, 3750, 5000 µg/mL test item with metabolic activation (Aroclor 1254-induced male Sprague-Dawley rat liver S9) and to 1873, 2497, 3727, 5000 µg/mL without metabolic activation for a harvest time of 20 and 12 hours respectively. Up to 200 first-division metaphase cells were scored at each dose level. Classes of aberrations included simple (breaks and terminal deletions), complex (rearrangements and translocations), and other (pulverized cells, despiralized chromosomes, and cells containing 10 or more aberrations). Negative and positive controls were performed satisfactorily. No increase in chromosomal aberrations was observed in cultured Chinese hamster ovary cells treated with up to 5000 μg/mL methyl ethyl ketoxime, with or without S9.