Ametryn

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1989

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Well documented, according to accepted guidelines

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1999

Report date:

1999

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Ametryn

EC Number:

212-634-7

EC Name:

Ametryn

Cas Number:

834-12-8

Molecular formula:

C9H17N5S

IUPAC Name:

N2-ethyl-6-(methylsulfanyl)-N4-(propan-2-yl)-1,3,5-triazine-2,4-diamine

Details on test material:

- Name of test material (as cited in study report): Ametryn; N2-ethyl-N4-isopropyl-6-methylthio-1,3,5-triazine-2,4-diamine
- Physical state: powder
- Analytical purity: 96.3%
- Lot/batch No.: 83200018
- Expiration date of the lot/batch: April, 2002
- Storage condition of test material: Stored at ambient temperature

Test animals

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Toxicology Department Rallis Research Center, Bangalore - 560 058, INDIA
- Age at study initiation: 6 months and above
- Weight at study initiation: 2.50 - 3.56 kg
- Housing: housed individually in 3 tier all aluminum cages with wire mesh bottom and common self draining litter trays
- Diet (e.g. ad libitum): ad libitum, Pelleted rabbit food ("Gold Mohur" brand) manufactured by Brooke Bond Lipton India ltd
- Water (e.g. ad libitum): ad libitum, protected, deep bore-well water passed through activated charcoal filter and exposed to UV rays in Aquaguard on-line water filter-cum-purifier
- Acclimation period: 15 days under laboratory conditions after veterinary examination


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18-22 °C
- Humidity (%): 40-70 %
- Air changes (per hr): 12-15
- Photoperiod (hrs dark / hrs light):12/12

IN-LIFE DATES: From: 08-08-1997 To: 21-08-1997

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

CMC (carboxymethyl cellulose)

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: Precisely weighed 0.750/0.375 * (low dose), 2.250/1.25 * (mid dose) and 4.500/2.250 * (high dose) of the finely ground test substance were individually suspended and the final volume made up to 150/75 mL * with 0.5% aqueous carboxy methyl cellulose in glass beakers to get the nominal concentrations of 5, 15 and 30 mg/mL of the suspension. The test substance suspensions were freshly prepared on each day of dosing. The homogeneity of the test substance suspensions during treatment was maintained by constant stirring using magnetic stirrers.
* for Batch 1 and 2 respectively


DIET PREPARATION
- Rate of preparation of diet (frequency): obtained from manufacturer
- Mixing appropriate amounts with (Type of food): not mixed with food


VEHICLE
- Concentration in vehicle: 0.5% aqueous solution with 1.0 mL/L of Tween 80
- Amount of vehicle (if gavage): dosage volume is 2 mL/kg bw
- Lot/batch no. (if required): 46789

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The stability and homogeneity of the test substance in the vehicle was analysed for the low and high dose groups before the start of the study. Precisely weighted 0.75 g (low dose) and 4.50 g (high dose) of the finely ground test substance were individually suspended and the final volume made up to 150 mL with 0.5% carboxy methyl cellulose to get the nominal concentrations of 5 and 30 mg/mL respectively of the suspension. The test substance suspensions were stirred continuously with a magnetic stirrer for 20 minutes before sampling. Samples for analysing the homogeneity were taken from top, middle, and bottom layers. One additional sample from the top layer was also drawn and stored at ambient temperature for 3 hours and analysed for stability of the suspension. The gavage samples were suitably diluted with acetone and the concentration of Ametryn Technical was analysed in GLC.

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1/1
- Proof of pregnancy: "successful mating" referred to as day 0 of pregnancy. (authors did not define successful mating).

Duration of treatment / exposure:

From day 6 to day 18 of gestation

Frequency of treatment:

Daily

Duration of test:

29 days (gestation days 0-6 = pre-treatment; gestation days 6-18 = treatment; gestation days 18-29 = post treatment).

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
10 mg/kg bw
Basis:
actual ingested

Doses / concentrations 2

Remarks:

Doses / Concentrations:
30 mg/kg bw
Basis:
actual ingested

Doses / concentrations 3

Remarks:

Doses / Concentrations:
60 mg/kg bw
Basis:
actual ingested

No. of animals per sex per dose:

22 females/group

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The doses selected were based on a range finding study completed prior to the final study. It was expected that the highest dose level would produce slight maternal toxic effects such as reduced maternal weight gains. The animals in the control group were handled in an identical manner to the test group.
- Rationale for animal assignment (if not random): random

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: twice daily


BODY WEIGHT: Yes
- Time schedule for examinations: initial body weight of all the rabbits included in the study were noted before mating. Body weights were noted on day 0, daily from day 6 through day 18 and on day 29 of gestation.


FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
Rabbits were given 500 g of food on day 0 of pregnancy. The food remaining on day 3 was weighed, recorded and replenished to 500 g. This procedure was repeated on days 6, 9, 12, 15, 18, 22, and 25. On day 29 of gestation the left over food was weighed.


WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No data


POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 29
- Organs examined: uterus and ovaries

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes

Fetal examinations:

- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: all per litter
- Skeletal examinations: Yes: all per litter
- Head examinations: Yes: all per litter

Statistics:

The litter was used as the basic sampling unit. The following statistical methods were used to analyse the various parameters:
1) Maternal body weight and weight gain, food intake, number of corpora lutea, number of implantations and mean fetal weight by Barlett's test followed by ANOVA and Dunnett's test.
2) Day 0 and absolute body weights by paired 't' test.
3) Number and percent (when required) of early and late resorptions, number of dead fetuses, number of abnormal fetuses, percent pre-implantation and post-implantation losses by Mann Whitney test.
4) Litter size and total number of fetuses by student's 't' test
5) Sex ratio, number of dams with any resorptions, number of dams with complete resorptions and incidence of malformations by 2x2 Contingency table (Chi-square test)
6) Number of fetuses with major malformations and number of dams with major malformed fetuses by 'Z' test.
7) The correlation between dose and response was analysed by student's 't' test.
All analyses and comparisons were evaluated at 5% (P=0.05) level.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
A decrease in body weight was noted on gestation day 18 in the 60 mg/kg bw/day dams. Body weight gain in the 60 mg/kg bw/day dams also was noted.
Gross Pathological findings of Dams: no statistically significant treatment-related effects

Effect levels (maternal animals)

Dose descriptor:

NOEL

Effect level:

30 mg/kg bw/day

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
The mean number of corpora lutea, implantations and the incidence of early and late resorptions in all the treatment groups were statistically comparable to the respective control values. While the incidence of pre-implantation loss in the treatment groups was comparable to the control value, the incidence of post-implantation loss showed a tendency towards an increase in the high dose group. There was an incidence of complete resorptions in the high dose group which was comparable to the historical data.

The total number of fetuses, the mean litter size, the number of male and female fetuses, the mean fetal weights and the sex ratio in the treatment groups were comparable to the respective control values. There was one incidence each of abnormal fetus in the high does group and dead fetus in the control group; however, these incidences were comparable to the historical data.
External observation, visceral observations, and skeletal observations : no statistically significant treatment-related effects

Effect levels (fetuses)

1

Dose descriptor:

NOEL

Effect level:

60 mg/kg bw/day

Basis for effect level:

other: embryotoxicity

2

Dose descriptor:

NOEL

Effect level:

60 mg/kg bw/day

Basis for effect level:

other: fetotoxicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified