Dimethyl methylphosphonate

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian germ cell study: cytogenicity / chromosome aberration

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: scientifically acceptable publication

Data source

Reference

Reference Type:

publication

Title:

Dimethyl methyl phosphonate induction of dominant lethal mutations in male mice

Author:

Dunnick JK, Solleveld HA, Harris MW, Chapin R and Lamb IV JC

Year:

1984

Bibliographic source:

Mutation Research 138: 213-218

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

compareable rodent dominat lethal assay

GLP compliance:

no

Remarks:

well documented study

Type of assay:

rodent dominant lethal assay

Test material

Test material information

Constituent 1

Reference substance name:

Dimethyl methylphosphonate

EC Number:

212-052-3

EC Name:

Dimethyl methylphosphonate

Cas Number:

756-79-6

Molecular formula:

C3H9O3P

IUPAC Name:

dimethyl methylphosphonate

Details on test material:

- Name of test material (as cited in study report): dimethyl methyl phosphonate (DMMP)
- Analytical purity: >99%
- Lot/batch No.: not specified; test substance was obtained from Stauffer Chemical Company, Weslport, Connecticut
- Other: the compound was analyzed by gas chromatography, thin-layer chromatography and by infrared, ultraviolet and nuclear magnetic resonance spectroscopy

Test animals

Species:

mouse

Strain:

other: CB6F1 males and CD-I females

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: B6C3F, male mice were obtained from Frederick Cancer Research Center (Frederick, MD), and were 7-8 weeks of age on the first day of dosing (referred to as day 1). Female CD-I mice were obtained from Charles River Breeding Laboratories (Portage, MI)
- Age at study initiation: the animals were 9 weeks of iage when mated
- Assigned to test groups randomly: yes
- Housing: housed in solid bottom polycarbonate cages with Corn Cob bedding (Granville Milling Co., Creedmoor, NC), Male mice were housed individually (except during mating) throughout the course of the study
- Diet (e.g. ad libitum): Open formula, autoclavable, rodent diet NIH 31 laboratory feed
- Water (e.g. ad libitum): tap water


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21.1±1.1°C
- Humidity (%): 50±10%
- Photoperiod (hrs dark / hrs light): a 12-h fluorescent light and dark cycle was provided

No additional data provided

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

- Vehicle(s)/solvent(s) used: water
- Justification for choice of solvent/vehicle: not specified
No additional data

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
Animals were dosed by gavage in aqueous solutions; no additinal details provided

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

5 days per week for 13 weeks

Post exposure period:

The 20 male mice in groups 1, 4, and 5 which were kept for an additional 15 weeks without chemical treatment, were mated to untreated CD-I female mice at week 29 (mating trial 4, days 196-200)

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 250, 500, 1000 and 2000 mg/kg bw
Basis:
actual ingested
male animals in goups listed below

No. of animals per sex per dose:

(1) vehicle control (40 animals); (2). 250 mg/kg (20 animals): (3) 500 mg/kg (20 animals; (4) 1000 mg/kg (40 animals) and (5) 2000 mg/kg (40 animals)

Control animals:

yes, concurrent vehicle

Positive control(s):

none

Examinations

Tissues and cell types examined:

Sperm concentration and morphology, hormones and enzymes levels, dominant lethal effect

Details of tissue and slide preparation:

Not applicable

Evaluation criteria:

Significant dominant lethal effect in male mice causing an increased number of dead implants (resorptions) and a decreased number of live fetuses when male mice treated for 4, 8, or 12 weeks, were mated to untreated female mice.

Statistics:

Statistical analysis for differences in mean number of live and dead implants and percent dead implants was done according to the Kruskal—Wallis one-way analysis of variance by ranks and the Wilcoxon rank sum test.

Results and discussion

Test results

Sex:

male/female

Genotoxicity:

positive

Remarks:

increased number of dead implants (resorptions) and a decreased number of live fetuses at 2000 mg/kg bw and somewhat at 1000 mg/kg, reversible after 15 weeks recovery

Toxicity:

no effects

Remarks:

no chemically related effects observed in treated animals

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

not examined

Additional information on results:

MORTALITY AND CLINICAL SIGNS
All male mice dosed with 0, 250, 500, 1000 or 2000 mg/kg DMMP, S days per week for 13 weeks, survived the treatment, and no dose-related clinical signs of toxicity were seen in any groups.

BODY WEIGHT
There were no chemically related effects on total body weight

ORGAN WEIGHT
There were no chemically related effects on organ/body weight ratios for testis, epididymis, prostate, and kidney

GROSS PATHOLOGY
Gross lesions were not seen in any group.

HISTOPATHOLOGY
Microscopic examination of selected organs, including those of the genitourinary tract did not reveal any treatment-related lesions. Dose-related effects were not seen on sperm concentration, sperm morphology, cholinesterase plasma levels, or FSH or LH plasma level

OTHER
- Mating frequency: the percentage of males able to impregnate at least 1 female was equal to or greater than 85% for each treatment group. The fertilization rate (number of fertilized females/number of females mated X 100) was equal to or greater than 85% in all groups of mice during the 4 mating trials, with the exception of the 250-mg/kg group at mating trial 1 where the fertilization rate was 75%. Chemical treatment had no effect on the fertilization rate (Table 1).

- Fertility: mating of control male B6C3F, mice to CD-1 females gave a reproducible number of live fetuses per female and a low background frequency of resorptions. The average number of live fetuses per female in the vehicle control group for mating trials 1-4, was 11.8, 10.3, 11.2 and 11.1, respectively. The average number of resorptions per female in the vehicle control group was 0.6, 1.0, 0.8 and 0.4 for mating trials 1-4. These mating trials occurred when male mice were 11-36 weeks of age and there were no age-related effects on fertility of the male mouse during this time period.

Test substance treatment of male mice at 2000 mg/kg for 4, 8, or 12 weeks decreased the average number of live fetuses per female and increased the average number of dead implants (resorptions) per female. The resorptions were primarily early resorptions. An increase in the number of dead implants was seen in the l000 mg/kg group in mating trials 1 and 3, but not at mating trial 2. The dominant lethal index was increased in the 2000 mg/kg group in mating trials 1-3 (40, 37, 44%, respectively), and in the 1000 mg/kg groups in mating trials 1 and 3 (12 and 13%, respectively). After a 15-week recovery period the percent dead implants in the 1000 and 2000 mg/kg groups returned to a rate comparable to that in the control groups (Table 1)

Any other information on results incl. tables

 

Table 1: Dominant lethal test with B6C3F1 male mice treated with test substance and mated to intreated CD-1 female mice (a)

Evaluated parameters	Test substance dose (mg/kg bw per day)
	0	250	500	1000	2000
1. Mating after 4 weeks of treatment
Males with pregnant females (%)	100% (20/20)	85% (17/20)	100% (20/20)	100% (20/20)	95% (19/20)
Mean fertilization rate (b)	85% (34/40)	75% (30/40)	88% (35/40)	85% (34/40)	85% (34/40)
Mean live implants/female (c)	11.9±0.3	12.2±0.3	11.4±0.4	10.4±0.5*	7.2±0.6**
Mean dead implants/female (c)	0.6±0.2	0.8±0.2	1.1±0.2*	1.6±0.3**	3.2±0.4**
Mean percentage of dead implants/female (in %) (d)	5.3±1.3	5.8±1.2	9.6±1.4*	13.4±2.2**	30.9±4.2**
Mean percentage of dominant lethal mutations (in %) (e)	-	-3	4	12*	40**
2. Mating after 8 weeks of treatment
Males with pregnant females (%)	100% (20/20)	100% (20/20)	100% (20/20)	100% (20/20)	100% (20/20)
Mean fertilization rate (b)	88% (34/40)	90% (36/40)	88% (34/40)	95% (38/40)	92% (37/40)
Mean live implants/female (c)	10.3±0.5	11.4±0.5	11.2±0.4	10.5±0.5	6.5±0.4**
Mean dead implants/female (c)	1.1±0.2	0.7±0.1	0.7±0.2	1.1±0.2	3.7±0.3**
Mean percentage of dead implants/female (in %) (d)	9.8±2.1	6.5±1.4	6.1±1.6	10.1±1.7	34.6±3.2**
Mean percentage of dominant lethal mutations (in %) (e)	-	-10	-8	-2	37**
3. Mating after 12 weeks of treatment
Males with pregnant females (%)	100% (40/20)	95% (20/20)	100% (20/20)	100% (20/20)	95% (38/40)
Mean fertilization rate (b)	94% (74/80)	92% (37/40)	90% (36/40)	88% (34/40)	89% (71/80)
Mean live implants/female (c)	11.2±0.4	10.9±0.5	11.1±0.6	9.7±0.5**	6.3±0.3**
Mean dead implants/female (c)	0.8±0.1	0.8±0.3	0.8±0.2	1.7±0.3**	4.7±0.2**
Mean percentage of dead implants/female (in %) (d)	8.3±1.5	8.3±2.9	6.6±1.8	15.3±2.7**	44.2±2.3**
Mean percentage of dominant lethal mutations (in %) (e)	-	3	1	13**	44**
4. Mating after 15 weeks of recovery
Males with pregnant females (%)	100% (20/20)	-	-	100% (20/20)	100% (20/20)
Mean fertilization rate (b)	90% (36/40)	-	-	92% (37/40)	95% (71/80)
Mean live implants/female (c)	11.1±0.4	-	-	11.4±0.3	11.1±0.4
Mean dead implants/female (c)	0.4±0.1	-	-	0.5±0.1	0.7±0.1
Mean percentage of dead implants/female (in %) (d)	5.0±1.6	-	-	4.5±1.1	6.2±1.4
Mean percentage of dominant lethal mutations (in %) (e)	-	-	-	-3	0
(a)20 males in each group, each male mated to 2 females except in the third mating trial where there were 40 males in the control and 2000 mg/kg groups; (b)Fertilization rate(number of fertilized females/number of females mated x 100); (c)% resorptions = (total dead implants/total dead and live implants)x100; (d)Mean±SE; (e)Percentage of induced dominant lethal mutations was calculated as: % dominant lethal mutations = (1-average living implants in test group/average living implants in control groupx100); *P<0.05; **P<0.01