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

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Type of information:

experimental study

Adequacy of study:

key study

Study period:

February 19, 1991

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Remarks:

A standard NTP (National Toxicology Program) protocol. No data on GLP.

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Unnamed

Year:

1991

Reference 2

Reference Type:

publication

Title:

Unnamed

Year:

1999

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Deviations:

yes

Remarks:

(no positive control was performed)

GLP compliance:

not specified

Type of assay:

micronucleus assay

Test material

Test material information

Constituent 1

Reference substance name:

Butanone oxime

EC Number:

202-496-6

EC Name:

Butanone oxime

Cas Number:

96-29-7

Molecular formula:

C4H9NO

IUPAC Name:

butan-2-one oxime

Details on test material:

- Name of test material (as cited in study report): Methyl Ethyl Ketoxime

Test animals

Species:

mouse

Strain:

B6C3F1

Sex:

male/female

Administration / exposure

Route of administration:

oral: drinking water

Vehicle:

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

Duration of treatment / exposure:

13 weeks.

Frequency of treatment:

Daily.

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 ppm

Doses / concentrations 2

Dose / conc.:

625 ppm

Remarks:

Equivalent to 110 and 145 mg/kg.bw/day in male and female mice respectively.

Doses / concentrations 3

Dose / conc.:

1 250 ppm

Remarks:

Equivalent to 200 and 340 mg/kg-bw/day in male and female mice respectively.

Doses / concentrations 4

Dose / conc.:

2 500 ppm

Remarks:

Equivalent to 515 and 630 mg/kg-bw/day in male and female mice respectively.

Doses / concentrations 5

Dose / conc.:

5 000 ppm

Remarks:

Equivalent to 755 and 1010 mg/kgw-bw/day in male and female mice respectively.

Doses / concentrations 6

Dose / conc.:

10 000 ppm

Remarks:

Equivalent to 1330 and 3170 mg/kgw-bw/day in male and female mice respectively.

No. of animals per sex per dose:

5 animals per sex per dose.

Control animals:

yes, concurrent vehicle

Positive control(s):

none;

Examinations

Tissues and cell types examined:

Mouse peripheral blood erythrocytes

Details of tissue and slide preparation:

At the end of the 13-week drinking water study, blood samples were obtained from male and female mice. Smears were immediately prepared and fixed in absolute methanol. The methanol-fixed slides were stained with a chromatin-specific fluorescent dye (acridine orange) and coded. Slides were scanned to determine the frequency of micronuclei in 2,000 normochromatic eythrocytes (NCEs) in each of 5 animals per exposure group

Evaluation criteria:

An individual trial is considered positive if the trend test P value is less than or equal to 0.025 or if the P value for any single exposure group is less than or equal to 0.025 divided by the number of exposure groups. A final call of positive for micronucleus induction is preferably based on reproducibly positive trials. Results of the 13-week studies were accepted without repeat tests, because additional test data could not be obtained. Ultimately, the final call is determined by the scientific staff after considering the results of statistical analyses, the reproducibility of any effects observed, and the magnitudes of those effects.

Statistics:

The frequency of micronucleated cells among NCEs was analyzed by a statistical software package that tested for increasing trend over exposure groups with a one-tailed Cochran-Armitage trend test, followed by pairwise comparisons between each exposure group and the control group In the presence of excess binomial variation, as detected by a binomial dispersion test, the binomial variance of the Cochran-Armitage test was adjusted upward in proportion to the excess variation

Results and discussion

Test results

Key result

Sex:

male/female

Genotoxicity:

negative

Remarks:

(up to 10000 ppm)

Toxicity:

not specified

Vehicle controls validity:

valid

Negative controls validity:

not examined

Positive controls validity:

not examined

Any other information on results incl. tables

Frequency of Micronuclei in Peripheral Blood Erythrocytes of Mice Following Treatment with Methyl Ethyl Ketoxime in Drinking Water for 13 Weeks:

A79779 -1

Start Date	Sample Collection Time	Sex		Cell	Methodology Used	Dosing Regimen	Route	Trend Test P-Value
02/19/1991	0 Hours	Female		NCE	Slide Scoring	WATER x 93, 93 Days	Dosed-Water	0.998
					Dose (ppm)	Number of Animals Scored	Mean MN-NCE/1000 NCE ± SEM	Pairwise P
Vehicle Control			Water		0	5	2.00 ± 0.35
Test Chemical			Methyl ethyl ketoxime		625	5	2.10 ± 0.58	0.4379
					1250	5	3.00 ± 0.42	0.0784
					2500	5	2.90 ± 0.89	0.0990
					5000	5	1.90 ± 0.37	0.5637
					10000	5	0.80 ± 0.34	0.9884

A79779 -2

Start Date	Sample Collection Time	Sex	Cell	Methodology Used	Dosing Regimen	Route	Trend Test P-Value
02/19/1991	0 Hours	Male	NCE	Slide Scoring	WATER x 92, 92 Days	Dosed-Water	1.000
				Dose (ppm)	Number of Animals Scored	Mean MN-NCE/1000 NCE ± SEM	Pairwise P
Vehicle Control		Water		0	5	4.80 ± 0.68
Test Chemical		Methyl ethyl ketoxime		625	5	4.50 ± 0.76	0.6224
				1250	5	4.00 ± 0.16	0.8036
				2500	5	3.70 ± 0.34	0.8841
				5000	5	1.40 ± 0.37	10.000
				10000	5	1.60 ± 0.19	10.000

NCE=normochromatic erythrocyte

Applicant's summary and conclusion

Conclusions:

No increase in the frequency of micronucleated normochromatic erythrocytes was observed in the peripheral blood of male or female mice administered methyl ethyl ketoxime via drinking water at concentrations from 625 to 10000 ppm for 13 weeks.

Executive summary:

A Mammalian Erythrocyte Micronucleus Test was performed on methyl ethyl ketoxima according to NTP's standard protocol (test method similar to OECD Guideline 474). 5 mice per sex and per dose were exposed to test item at 0 (control, water), 625, 1250, 2500, 5000 and 10000 ppm (0, 110, 200, 515, 755, 1330 mg/kg bw/day males and 0, 145, 340, 630, 1010, 3170 mg/kg bw/day females) for 13 weeks by drinking water. At the end of the exposure, blood samples were obtained from male and female mice, smears were prepared, fixed in absolute methanol and stained with a chromatin-specific fluorescent dye (acridine orange). Slides were scanned to determine the frequency of micronuclei in 2000 normochromatic eythrocytes (NCEs) in each of 5 animals per exposure group. No increase in the frequency of micronucleated normochromatic erythrocytes was observed in the peripheral blood of male or female mice administered methyl ethyl ketoxime via drinking water at concentrations from 625 to 10000 ppm (1130 mg/kg bw/day males and 3170 mg/kg bw/day females) for 13 weeks. The percentage of normochromatic erythrocytes among the population of circulating erythrocytes was markedly decreased at the highest dose tested in male and female mice.