Diethylmethylbenzenediamine

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

June 2013 to July 2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: This GLP compliant study was performed in accordance with OECD test guideline 414 (2001) and Council Regulation (EC) No 440/2008 B.31 (2008). and in compliance with Good Laboratory Practice regulations.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2014

Report date:

2014

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

yes

Remarks:

The temperature of the animal room was 21±2oC instead of 22±2oC. There were slight deviations in the relative humidity of the animal room. Prior to sample aanalysis, the analytical method was validated using 3 spiked samples per dose level.

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Diethylmethylbenzenediamine

EC Number:

270-877-4

EC Name:

Diethylmethylbenzenediamine

Cas Number:

68479-98-1

Molecular formula:

C11H18N2

IUPAC Name:

diethylmethylbenzenediamine

Test material form:

other: Clear yellow liquid

Details on test material:

- Name of test material (as cited in study report): DETDA
- Physical state: Liquid
- Analytical purity: 97.8%
- Lot/batch No.: 4500051816-011110
- Storage condition of test material: Ambient temperature (15-25°C)

Test animals

Species:

rat

Strain:

Wistar

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan, Horst, The Netherlands
- Age at study initiation: 11 weeks female, 12 weeks male
- Weight at study initiation: Not reported
- Housing: During the quarantine and acclimatization periods, the animals were housed in groups of 4 per sex. For mating, one male and two females were housed together. Mated females were housed individually in macrolon cages.
- Diet (e.g. ad libitum): Cereal-based (closed formula) rodent diet ad libitum from the arrival of the rats until the end of the study.
- Water (e.g. ad libitum): ad libitum from the arrival of the rats until the end of the study.
- Acclimation period: approx 2 weeks quarantine/acclimation

ENVIRONMENTAL CONDITIONS
- Temperature (°C): The room was maintained at a temperature of 19-23 deg C.
- Humidity (%): Between 43.7 and 69.7%, and in four occasions higher (72.9, 74, 76.8 and 79.5%, respectively) for short periods.
- Air changes (per hr): 10 air changes per hour
- Photoperiod (hrs dark / hrs light): 12 hours dark and 12 hours light

Administration / exposure

Route of administration:

oral: feed

Details on exposure:

DIET PREPARATION
The test substance was administered in the powder diet (to the selected mated females only). The test item was incorporated in the basal diet by mixing in a mechanical blender. One batch of experimental diets was prepared on 28 June 2013 shortly before the start of the study. After preparation, the experimental diets were divided into amounts of diets that were stored in plastic bags in a freezer (<-18°C). Twice weekly, the amount of diet required per lot per group was removed from the freezer to feed the animals. The feed was provided as a powder in stainless steel cans, covered by a perforated stainless steel plate to prevent spillage.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The homogeneity, achieved concentration and the stability of the test substance in the rat feed were analysed in the batch of diets prepared for this study. Directly after mixing of each diet, samples for the homogeneity and stability experiments were taken from the mixer.
Five samples of each group were taken in the order: top left, top right, top centre, middle centre, bottom centre for determination of homogeneity and dose confirmation.
Samples for determination of stability of the test substance in the rat feed were taken after five days in the animal room and after storage for 5 weeks in a freezer at <-18°C.

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1 male to 2 females per cage
- Length of cohabitation: 5 days of mating
- Proof of pregnancy: [vaginal plug / sperm in vaginal smear] referred to as day 0 of pregnancy
- Any other deviations from standard protocol:

Duration of treatment / exposure:

Pregnant females received the test substance via diet throughout gestation days 0-20.

Frequency of treatment:

Daily

Duration of test:

Up to and including gestation day 20.

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0, 50, 150 and 500 mg/kg bw/day
Basis:
nominal in diet
Target concentration

Doses / concentrations 2

Remarks:

Doses / Concentrations:
0, 3.66, 10.59 and 27.96 mg/kg bw/day
Basis:
nominal conc.
Mean test substance intake based on nominal dietary levels

Doses / concentrations 3

Remarks:

Doses / Concentrations:
0, 2.63, 7.83 and 20.45 mg/kg bw/day
Basis:
actual ingested
Mean test substance intake based on actual dietary levels

No. of animals per sex per dose:

24 females

Control animals:

yes, plain diet

Details on study design:

- Dose selection rationale: The dose levels were selected on the basis of two dose range finding studies with the test substance in pregnant rats
- Rationale for animal assignment: The mated females were randomized over the 4 experimental groups whereby animals from the same day of pregnancy were equally distributed over all groups as far as possible. After 5 days of mating, the desired total of 96 mated females (24 females per group) were randomized into the different groups in daily lots. Care was taken that females mated by the same male were not placed in the same experimental group.
Sperm positive females that turned out to be non-pregnant were killed not earlier than 21 days after copulation. Surplus mated females and females that did not show evidence of copulation after 5 days of mating were also housed individually until sacrifice (not earlier than 21 days after the last day of the mating period). Males were used for mating only and were not included in the study.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily cage side observations in the mornings and in the afternoons during the week day. One check per day was performed during the weekend.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: see cage side observations

BODY WEIGHT: Yes
- Time schedule for examinations: Gestation days 0, 3, 7, 10, 14, 17, 20 and 21.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- The food consumed for each selected, mated female was measured over the periods: gestation days 0-3, 3-7, 7-10, 10-14, 14-17 and 17-20. The results are expressed in g per animal per day and g per kg body weight per day.
- Test substance intake during gestation, based on the intended dietary levels was calculated for each intervall and averaged to nominal concentrations of 3:66, 10.59 and 27.96 mg/kg BW/ day. Upon analysis of the experimental diets it appeared that the initial actual content of test substance in the diets may have been lower, and that the test substance was not stable when the test diets were moved to the animal room in an open container. Therefore, the test substance intake is presented taking into account both the lower initial actual levels and the (extrapolated) loss during storage for 3 or 4days in the animal room during feeding. (diets were replaced by fresh diets twice per week) . The calculations were based on the test substance analysis in the diet. The extrapolated actual mean test substance intake during gestation (gestation day 1-20) was calculated to be 2.63, 7.83 and 20.45 mg/kg body weight per day in the low, mid and high dose group, respectively).

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day #21
- Organs examined: At necropsy blood was collected for haematology and clinical chemistry. Necropsy parameters included gross examination of the dam, all organs were examined for gross abnormalities. At autopsy maternal tissues showing macroscopic anomalies were sapled and fixed for further microscopic examination if needed. Uterus weight (full and empty), ovary weight and number of corpora lutea and histopathological examination of the pancreas were performed. The number of implantation sites, early and late resorptions, live and dead fetuses, fetus weight, placenta weight, fetus sex and external abnormalities were recorded. Pre-implantation loss and post-implantation loss were calculated.

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- 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: half per litter
- Skeletal examinations: Yes: half per litter
- Head examinations: Yes: half per litter

Statistics:

Tests were performed as two sided tests: Significance was defined on the basis of p< 0.05 5* or p<0.01 (**). Continous data were subjected to a decision tree for continous data; consiting of the Shapiro Wilks test for normality, the Levines test; Anova or Kruskall Walis tests depending on the distribution; followed by Dunretts or Dunns test, and dichotomous data to a decision tree for dichotomous data consisiting of the Fisher Chi square Test followed by the Fisher exact test if p< 0.05. Inzidences of histopathological changes were analysed by Fishers exact probability test.

Indices:

The following indices were calculated:
female fertility index: (No of pregnant females/ No: of inseminated females) x 100
pre-implantation loss: ((No of corpora lutea - No of implantation sites) / No. of corpora lutea) x 100
post-implantatiion loss: ((No of implantation sites - No of life fetusses) / No of implantation sites) x 100
gestation index: (No of females with life fetusses / No of females pregnant) x 100
sex ratio: (No of live male fetuses / no of live fetuses) x 100

Historical control data:

Comparisons with historical control data of the same institute and same strain of rats were made as appropriate:

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes. Remark: Body weight gain and histopathological changes in the pancreas.

Details on maternal toxic effects:
In the high dose group mean body weight was decreased compared to controls in the first 3 days of gestation. Body weight gains in the high dose group were statisitcally significantly decreased in the high dose group compared to controls. Mean food consumption was decreased in the high dose group throughout gestation. A dose dependent induction of acinar cell apoptosis and mononulear cell inflammation of the pancreas; the pri,ary target organ of DEDTA toxicity, was observed in the mid qnd high dose groups. The findings in the pacreas histopathology in the mid dose group were observed in 3 animals and were graded minor, while they were significant in the high dose group:

Effect levels (maternal animals)

Dose descriptor:

NOEL

Effect level:

2.63 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes. Remark: in the presence of severe maternal toxicity

Details on embryotoxic / teratogenic effects:
Cesarian section data:
The mean number of corpora lutea was comparable in all groups (13.6, 13.6, 13.2 and 13.2 for the control group, low dose, mid dose and high dose group, respectively).
Mean pre-implantation loss was increased in the high dose group (5.5, 6.7, 12.4 and 31.1% for the control, low, mid and high dose group, respectively) (Historical control data range: 5.5 – 16.8). The mean number of implantations per animal was statistically significantly decreased in the high dose group (12.9, 12.7, 11.4 and 9.5 for the control, low, mid and high dose group, respectively) (historical control data range: 10.9 – 12.9).
The mean number of fetuses was decreased in the high dose group (12.2, 12.1, 10.9 and 8.7 per animal for the control, low, mid and high dose group, respectively) (Historical control data range: 10.1 – 12.2).
The mean number of early resorptions per rat (0.7, 0.5, 0.5 and 0.6) and late resorptions (0.0, 0.1, 0.1 and 0.1 for the control , low, mid and high dose group, respectively) was comparable in all groups. No dead fetuses were observed in this study.

A lower mean number of implantations and live fetuses as well as a higher pre-implantation loss in the high dose group were considered to be treatment related and were considered to be related to the maternal toxicity observed at this dose level.

Fetus weight and sex:
The mean percentage of male fetuses per litter was statistically significantly increased in the high dose group (41.6, 46.4, 49.1 and 56.8 for the control, low, mid and high dose group, respectively). However, this was considered not biologically relevant and was related to a relative low percentage of males in the control group (Historical control data range: 41.6 – 52.7).
A statistically significantly lower mean fetus weight was observed in the high dose group (4.33, 4.27, 4.24 and 3.89 g for the control, low, mid and high dose group, respectively.
(Historical control data range: 4.2 – 4.7)

These findings were considered to be related to maternal toxicity.

Placental weight
Mean placenta weight was 0.46, 0.47, 0.47 and 0.43 g for the control, low, mid and high dose group, respectively. Historical control range: 0.45 – 0.51. Placentaweight was slightly lower in the high dose group as compared to the control group. When reported per sex, for female fetuses mean placenta weight was statistically significantly decreased in the high dose group.

This effect was considered to be related to maternal toxicity.

External observations:
Malformations:
no external malformations were observed in any dose group.
Variations:
External variations
Fifteen fetuses in the high dose group (from two litters) were observed to be small at necropsy. The other external findings were considered unremarkable. Three fetuses (from different litters) in the mid dose group were small, two fetuses in the mid dose group were pale and several fetuses in all groups (3, 4, 2 and 1 in the control, low, mid and high dose group, respectively) showed subcutaneous hemorrhages.

Visceral observations:
Visceral malformations
Malformations in the lens were observed in all groups (1, 1, 5 and 3 fetuses in the control, low, mid and high dose group, respectively).
Based on the low incidence and distribution over the groups, this was not considered to be treatment-related.
One fetus in the mid dose group showed a hernia ventralis. Another fetus in the mid dose group was too small (0.567 gram) to determine sex and perform detailed visceral examinations. Based on size and weight, this fetus was determined severely small and was classified malformed.
Based on single incidences, these observations were considered not treatment-related.

Visceral variations
Variations included dilated ventricles of the brain, discolored content of the stomach, blood-filled pericardium, fold retina, variations in the ureters, distended urinary bladder and dilation of the renal pelvis.
Based on the low incidence and distribution of these observations over the groups, these variations are not considered treatment-related.

Skelatal observations:
Skeletal malformations
No skeletal malformations were observed.

Skeletal variations
Skeletal variations included variations in ossification of the skull, sternebrae, phalanges, digits,metatarsals, cervical bodies and variations in the ossification and number of ribs.
The incidence of unossified metatarsals in the high-dose group was statistically significantly increased as compared to the control group and could be indicative for a retardation in ossification related to the small size and weight of the pups in the high dose group.

In conclusion, based on the incidence and distribution of the malformations and variations no treatment-related adverse effects were observed in visceral and skeletal examination of the foetuses. An increase in incidence of unossified metatarsals in the high dose group could be related to the lower pup weight and maternal toxicity in this group.

Effect levels (fetuses)

Dose descriptor:

NOAEL

Effect level:

7.83 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: fetotoxicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

In a developmental toxicity study in rats according to OECD TG 414 and GLP groups of 24 pregnant rats received dietary doses of 0, 2.63, 7.83 and 20.45 mg/kg bw per day from day 0 to day 20 of gestation. The study included in addtion to the parameters normally investigated in a developmental toxicity study a histopathological investigation of the pancreas of the dams of all dose groups, due to the known target organ toxicity of the substance. In the high dose group signs of pronounced maternal toxicity were observed that included loss of body weight during the first three days of gestation and a statistically significant reduction in body weight gain compared to concurrent controls throughout the study. Histopathology of the pancreas of the high dose animals revealed minimal to moderate diffuse apoptosis of the acinar cells in 13 of 24 animals and mild to moderate mononulear intertitial inflammation in 15 of 24 animals. In the mid dose dams minimal diffuse apoptosis of the acinar cells was observed in 2 of 24 animals and minimal mononulear intertitial inflammation in 1 of 24 animals.
Based on the effects on the pancreas the maternal NOEL was 2.63 mg/kg bw/day.
Statisically significant test substance related effects on embryofetal development were only observed at the high dose level and included a decreased pre-implanatation loss, decreased mean number of implantations per animal, decreased mean number of live fetuses and a lower mean fetal and placental weights and an increased number of small fetuses. No test substance related external, viceral or skeletal malformations were observed in any of the dose groups, except for a slightly retarded ossification in the high dose group that was related to lower pup weight and maternal toxicity. The developmental effects observed in this study, are typical effects that occur secondary to maternal toxicity as described by Waalkens-Berendsen et al., 2002 and 2004, Wolterbeek et al., 2004 and Meiling et al., 2004. The developmental NOAEL in this study was at the mid dose group of 7.83 mg/kg bw/d. As the effects observed can be regarded as secondary to maternal toxicity, no classification for developmental toxicity is proposed.

References quoted:
Waalkens-Berendsen D.H., Kuilman-Wahls M.E.M., Wolterbeek A.P.M. Maternal toxicity and fetal development: effects of decreased food intake.
Reproductive Toxicology 16, 425, 2002.

Wolterbeek APM, Tegelenbosch-Schouten MM, Waalkens-Berendsen DH and Dijkstra A.
Impact of maternal toxicity on pre- and postnatal development of rats.
Reproductive Toxicology 18, 753, 2004.

Meiling J, Wolterbeek APM, Waalkens-Berendsen DH, Tegelenbosch-Schouten MM and Dijkstra A. Impact of maternal toxicity on pre- and postnatal development of rats.
Toxicology and Applied Pharmacology 197, 211, 2004.

Waalkens-Berendsen ID, Tegelenbosch-Schouten MM, Dijkstra A and Wolterbeek APM.
Impact of maternal toxicity on pre- and postnatal development of rats.
The Toxicologist 78, Suppl. 1, 221, 2004

Executive summary:

A developmental toxicity study was conducted with Diethylmethylbenzene diamine (DEDTA) accoring to OECD TG 414 (2001) and Council Regulation EC No. 440/2008 B.31 (2008). Groups of 24 pregnant rats received DEDTA by continuous oral administration in the diet from gestation day (GD) 0 until GD 20. The test substance was given at constant dietary nominal concentrations of 0 (control), 50 (low-dose), 150 (mid-dose) and 500 mg/kg diet (high-dose). These doses corresponded to 0, 2.63, 7.83 and 20.45 mg/kg bw per day. During the in-life phase clinical signs, maternal body weight and food consumption were recorded. Ophthalmoscopic examination was performed pre-treatment and at gestation day 20. At Caesarean section, females and fetuses of all groups were macroscopically examined and blood was collected for haematology and clinical chemistry. Fetuses, placentas and reproductive organs were weighed. Histopathology of the pancreas as the primary target organ for DEDTA toxicity was performed in the dams. Fetuses were further processed for fetopathological examination.

 

Upon analysis of the experimental diets, DETDA was found to be homogeneously distributed at all dose levels and stable in diets after storage in a freezer (≤ - 18ºC). However, the initial measured content of DETDA was 10-16% lower than intended, and storage in the animal room for 5 days (in an open container) resulted in 32-41% loss. Although the measured concentrations were lower than the intended nominal concentrations in diets, the achieved exposure levels did result in maternal toxicity at the high dose level. Therefore the guideline requirements of maternal toxicity at the high dose level were met and the study was considered valid at relevant dose levels.

Feed was removed and completely replaced by feed from the freezer twice weekly at three or four day intervals. The actual test substance intake was assessed taking into account the measured initial levels and the (extrapolated) loss during storage for 3 or 4 days in the animal room.

In the high dose group maternal toxicity was observed as represented by a body weight loss during the first three days of gestation, followed by a decreased mean body weight gain and decreased food consumption during gestation, reduced ovary weight and induction of acinar cell apoptosis and mononuclear cell inflammation in the pancreas in most of the animals of the high dose group (13 animals with minimal to moderate apoptosis of the pancreatic acinar cells, 15 animals with minimal to mild mononuclear cell inflammation). In the mid dose group minimal induction of acinar cell apoptosis was observed in two animals and minimal mononuclear cell inflammation in one animal. Although this finding was of low incidence and severity in this group, it could  be regarded as a first indication of an effect on the target organ. Consequently, the low dose level was considered a No Observed Effect Level (NOEL) for maternal toxicity..

 

Developmental toxicity was observed in the high dose group, as evidenced by a decreased number of implantation sites and live fetuses. In addition mean placenta weight and mean fetus weight were decreased, which was confirmed by an increase in incidence of small fetuses. A slight retardation in ossification in the fetuses of the high dose group was related to the lower fetus weight.

 

Fetal observations with single incidences including one foetus showing a hernia ventralis, one fetus being too small and one fetus showing dilated ventricles of the brain were considered not treatement related based on the low (single) incidence and the absence of dose relationship.

 

In absence of developmental effects in the mid-dose group, the NOAEL for developmental toxicity was placed at the mid-dose level of 7.83 mg/kg bw/day

 

Effects on fetus weight, placenta weight and ossification are considered to be related to maternal toxicity as outlined in Waalkens-Berendsen et al., 2002 and 2004, Wolterbeek et al., 2004 and Meiling et al., 2004. In this study overt maternal toxicity was observed at the high dose level. An onset of the target organ effects in the dams was already observed in some animals of the mid dose group, but not accompanied by fetal toxicity.Consquently the effects on embryo-fetal development that were observed at the high dose level were considered to be secondary to maternal toxicity

 

 

References:

Waalkens-Berendsen D.H., Kuilman-Wahls M.E.M., Wolterbeek A.P.M. Maternal toxicity and fetal development: effects of decreased food intake.

Reproductive Toxicology 16, 425, 2002.

 

 

Wolterbeek APM, Tegelenbosch-Schouten MM, Waalkens-Berendsen DH and Dijkstra A.

Impact of maternal toxicity on pre- and postnatal development of rats.

Reproductive Toxicology 18, 753, 2004.

 

Meiling J, Wolterbeek APM, Waalkens-Berendsen DH, Tegelenbosch-Schouten MM and Dijkstra A. Impact of maternal toxicity on pre- and postnatal development of rats.

Toxicology and Applied Pharmacology 197, 211, 2004.

 

Waalkens-Berendsen ID, Tegelenbosch-Schouten MM, Dijkstra A and Wolterbeek APM.

Impact of maternal toxicity on pre- and postnatal development of rats.

The Toxicologist 78, Suppl. 1, 221, 2004