2-(3-oxazolidinyl)ethyl methacrylate

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

July 2, 2001 - July 19, 2001

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2002

Report date:

2002

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.3700 (Prenatal Developmental Toxicity Study)

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2-(3-oxazolidinyl)ethyl methacrylate

EC Number:

256-260-2

EC Name:

2-(3-oxazolidinyl)ethyl methacrylate

Cas Number:

46235-93-2

Molecular formula:

C9H15NO3

IUPAC Name:

2-(1,3-oxazolidin-3-yl)ethyl 2-methylprop-2-enoate

Test material form:

liquid

Remarks:

yellow

Test animals

Species:

rat

Strain:

other: Crl:CD BR

Details on test animals or test system and environmental conditions:

Eighty-eight timed-pregnant, nulliparous, Crl:CD BR rats were received from Charles River Laboratories, Kingston, NY on June 28 and 29, 2001. The animals were Gestation Day (G) 1 or 2 upon receipt. Mature females were naturally mated with mature males at the Charles River facility. The day of conception was designated as G0. Mature males of the same strain of rats were used.
All animals were weighed on arrival and assigned an ear tag bearing the animal's permanent and unique identification number. Cage cards indicating protocol number, group number, dose level, test substance and unique identification number were also assigned to all animals following randomization into test groups.
Upon arrival, the female rats were placed in a pre-sanitized room. Routine animal care procedures of the Laboratory Animal Service Unit (SOP 10) were in effect for the duration of the study. Each rat was housed individually in a suspended, stainless steel cage (approximately 18 x 18 x 34 cm) above absorbent paper that was changed approximately 3 timeslweek. PMI Certified Rodent Diet 5002 (meal) was offered ad libitum. All rats had ad libitum access to water (via automatic watering) purified by reverse osmosis. The study room was environmentally controlled with controls set to maintain a temperature of approximately 23°C with a relative humidity range of 30-70%. The temperature and relative humidity were monitored 24 hrs a day. During the study, the average daily temperature was approximately 22°C and the relative humidity ranged from 46-65%. Any minor excursions that occurred from these ranges were not considered to have any adverse effect on the conduct of this study. Temperature and humidity remained in compliance with acceptable ranges defined in the "Guide for the Care and Use of Laboratory Animals" ISBN No. 0-309-05377-3, Revised 1996. An automatically controlled 12 hr lightldark cycle was maintained throughout the study.

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

Suspensions of the test material in corn oil were prepared twice during the study and administered by gavage on G6-19 at a volume of 5 mllkg of body weight. The control group was given the vehicle only (corn oil), using the same route, volume and dosing schedule. The total dose administered each day was based on the most recently recorded body weight of each animal. The test suspensions for each dose level were prepared in the following manner:
The appropriate amount of test substance was used to prepare sufficient quantities of 3 suspensions for administration at dose levels of 25, 100 and 300 mg a.i./kg. Dose preparation was conducted twice during the study. The test substance was weighed into a plastic beaker. Corn oil was added to reach the desired volume. A magnetic stirbar was added, the beaker was placed on a magnetic stirplate, and the suspension was stirred until visually homogenous. All suspensions were continuously stirred during dosing and sampling procedures. The suspensions were stored in a plastic-coated jar in the refrigerator. Each day's suspension was removed from the jar prior to daily dosing.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples from both dose preparations (each dose level) were analyzed for proximity to target. Homogeneity was determined by comparing the values for the top, middle, and bottom samples collected from the initial dose preparation from each test concentration. A duplicate set of all samples analyzed were collected and stored refrigerated at the testing facility. The samples were analyzed using Toxicology Analytical Group Test Method #0 1P- 106, "Analytical Procedure for Determining the Concentration of OXEMA in Corn Oil Dosing Suspensions", March, 2001. The 14-day stability of OXEMA in corn oil was confirmed in a concurrent study.

The analytical results confirm that:
1. The procedure used for dose preparation provided homogeneous mixtures of the test substance.
2. OXEMA concentrations were within +/-3% of nominal target concentrations for all levels.
3. Concentrations of OXEMA (refrigerated) were shown to be stable for 15 days in a concurrent study (Rohm and Haas Study No. 01P-070).

Details on mating procedure:

The animals were Gestation Day (G) 1 or 2 upon receipt. Mature females were naturally mated with mature males at the Charles River facility. The day of conception was designated as G0. Mature males of the same strain of rats were used.

Duration of treatment / exposure:

GD 6-19

Frequency of treatment:

daily

Duration of test:

until G20

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day (nominal)

Doses / concentrations 2

Dose / conc.:

25 mg/kg bw/day (nominal)

Doses / concentrations 3

Dose / conc.:

100 mg/kg bw/day (nominal)

Doses / concentrations 4

Dose / conc.:

300 mg/kg bw/day (nominal)

No. of animals per sex per dose:

22

Control animals:

yes, concurrent vehicle

Details on study design:

The rat was selected since it is the recommended rodent species in investigations of developmental toxicity. The Crl:CD BR strain of rat was chosen due to the extensive experience with and historical control data available for this strain at the testing facility and at the supplier.
OXEMA was administered by oral gavage because the dose can be quantitated easily and gavage is an accepted method of administering test material in a rat developmental toxicity study. The high dose was selected based on a range-finding study which showed that the dose level of 300 mg ai/kg would be an acceptable high dose for the developmental study and it induced sufficient maternal toxicity to preclude higher doses.
Females for this study were assigned to the control and treated groups using a randomization procedure which was based on stratified G3 body weights. After the females of each lot were assigned, the mean G3 body weight for each group was calculated, and the summary statistics for each group were examined for homogeneity.

Examinations

Maternal examinations:

The females were weighed on G3, 6, 9, 12, 15, 18 and 20. Clinical signs (dams were removed from the cage and examined) were performed daily through G20. The dams were also observed daily to detect dead or moribund animals. Each dam's feed consumption was measured from G3-6,6-9,9-12, 12-15, 15-1 8 and 18-20.

On G20, prior to terminal Cesarean section, animals were euthanized by asphyxiation with C02 gas. A limited necropsy was performed on all dams. During the necropsy, animals were examined for evidence of pregnancy (i.e., the number of corpora lutea and implantation sites were recorded), and gross lesions of the abdominal and thoracic cavities. Carcasses were discarded after necropsy.

Ovaries and uterine content:

Following maternal necropsy, each intact gravid and non-gravid uterus was weighed. The uterus was opened, and the number and position of live and dead fetuses and early and late resorptions were recorded, if present.

Fetal examinations:

Live fetuses were weighed, sexed, and examined for external alterations. All live fetuses were euthanized by lethal i.p. injection of Nembuta(lAbbott Laboratories, North Chicago, IL). Alternating live fetuses from each litter were examined for soft tissue alterations using the Staples' Technique. In addition, fetuses with external abnormalities were examined for soft tissue anomalies. The heads from fetuses receiving soft tissue exam were fixed in Bouin's fixative and examined using the technique of Barrows and Taylor. Fetuses receiving soft tissue exams were discarded after evaluation. Skeletal staining (i.e., using alizarin red S) was performed on all remaining fetuses. The stained fetuses were examined for skeletal alterations. Fetuses that had both visceral and skeletal evaluations received a skeletal examination of the body only.

Statistics:

The litter (the proportion of affected fetusesllitter or the litter mean) was considered the experimental unit for the purpose of statistical evaluation. The level of significance selected was p < 0.05. A pair-wise test between the control and treated groups was applied to each parameter.

2xN Chi-square test was used for evaluation of incidence of pregnancy, adult necropsy findings, incidence of maternal death, and litters with total resorptions.
When the 2xN Chi-square test is significant, Fisher's exact test with a Bonferroni correction for multiple comparisons will be used to detect significant differences between each treated group and the vehicle control group.
ANOVA was used for evaluation of maternal body weight, maternal body weight change, feed consumption, fetal body weight, gravid uterine weight.
When the one-way ANOVA is significant, Dunnett's test will be used to detect significant differences between each treated group and the vehicle control group.
2xN Kruskal-Wallis nonparametric ANOVA was used for evaluation of implantations, live fetuses, dead fetuses, resorptions (early and late), corpora lutea, and incidence of fetal alterations.
When the 2xN Kruskal-Wallis nonparametric ANOVA is significant, 2x2 Kruskal-Wallis nonparametric ANOVA with a Bonferroni correction for multiple comparisons will be used to detect significant differences between each treated group and the vehicle control group.

All maternal and fetal examinations were conducted blind (i.e., prosectors did not know the dose group of the dam or fetus they were examining).

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

No treatment-related clinical signs of toxicity were observed in dams at any dose level. An increased incidence in salivation prior to dosing was noted in dams at 300 mg/kg. However, this was not considered treatment-related since it was only noted immediately prior to dosing.

Mortality:

mortality observed, treatment-related

Description (incidence):

Two females at 300 mglkg were found dead during the study. These deaths were considered treatment-related. Both animals experienced severe weight loss prior to death. No other mortalities occurred.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

There was no effect on maternal body weight in dams at dose levels up to and including 100 mg/kg. Mean gestation body weight at 300 mg/kg was decreased (5-10%) beginning on G9 through G20. Dams at 300 mg/kg lost weight initially (G6-9) and body weight gain during gestation remained depressed (30%) in females at 300 mg/kg throughout the dosing period (G6-20). A corresponding decrease (76%) in net weight change (i.e., net body weight change - uterine weight) was also noted at this level.

There was no effect on gravid uterine weight noted at any dose level.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

There were no treatment-related effects on feed consumption in dams at dose levels up to and including 100 mg/kg. Feed consumption was decreased (10-43%) throughout the dosing period (G6-20) in dams at 300 mg/kg.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

There were no treatment-related necropsy findings in dams at dose levels up to and including 100 mg/kg. Reddened and thickened stomachs were noted in dams at 300 mg/kg.

Maternal developmental toxicity

Pre- and post-implantation loss:

no effects observed

Total litter losses by resorption:

no effects observed

Early or late resorptions:

no effects observed

Dead fetuses:

no effects observed

Details on maternal toxic effects:

No treatment-related effects were noted in the number of viable litters, mean numbers of resorptions, live or dead fetuses or sex ratio per litter at any dose level.

Effect levels (maternal animals)

Dose descriptor:

NOEL

Effect level:

100 mg/kg bw/day

Based on:

act. ingr.

Basis for effect level:

body weight and weight gain

food consumption and compound intake

gross pathology

mortality

Results (fetuses)

Fetal body weight changes:

effects observed, treatment-related

Description (incidence and severity):

There were no treatment-related effects on fetal body weight among males, females or both sexes combined at dose levels up to and including 100 mg/kg. A statistically significant decrease (5%) in combined and male fetal body weight was noted at 300 mg/kg. This slight reduction in fetal body weight is most likely a secondary effect related to the decreased maternal weight gain seen at this dose.

External malformations:

no effects observed

Description (incidence and severity):

No treatment-related increases in the type or incidence of external, visceral or skeletal malformations were detected at any dose level. The malformations detected in this study were considered spontaneous due to their low incidence and lack of an doseresponse.

Skeletal malformations:

no effects observed

Description (incidence and severity):

No treatment-related increases in the type or incidence of external, visceral or skeletal malformations were detected at any dose level. The malformations detected in this study were considered spontaneous due to their low incidence and lack of an doseresponse.

No treatment-related increases were detected in the type or incidence of external, visceral or skeletal variations at dose levels up to and including 100 mg/kg. There was an increase (although not statistically significant) in skeletal variations noted in fetuses at 300 mg/kg. These included: reduced ossification of the parietals, supraoccipital and interparietal bones of the skull. While the increased incidence of reduced ossification was correlated with the maternal toxicity (and is considered secondary to) noted at this level (i.e., decreased body weight gain and feed consumption), a causal relationship can not be definitively established. It is clear that the fetus is not uniquely sensitive. The reduced ossification is considered to be related to the reduced fetal body weight. The other variations detected in this study were considered incidental because of their low occurrence rate.

Visceral malformations:

no effects observed

Description (incidence and severity):

No treatment-related increases in the type or incidence of external, visceral or skeletal malformations were detected at any dose level. The malformations detected in this study were considered spontaneous due to their low incidence and lack of an doseresponse.

Effect levels (fetuses)

Dose descriptor:

NOEL

Effect level:

100 mg/kg bw/day

Based on:

act. ingr.

Sex:

male/female

Basis for effect level:

fetal/pup body weight changes

Overall developmental toxicity

Developmental effects observed:

yes

Lowest effective dose / conc.:

300 mg/kg bw/day (nominal)

Treatment related:

yes

Relation to maternal toxicity:

developmental effects as a secondary non-specific consequence of maternal toxicity effects

Dose response relationship:

yes

Relevant for humans:

yes

Applicant's summary and conclusion

Conclusions:

OXEMA, when administered orally by gavage to presumed-pregnant rats on G6-19, produced no evidence of developmental toxicity in dose levels up to and including 100 mg a.i./kg/day. Some developmental effects (decreased fetal body weight and reduced cranial ossification) were seen at 300 mg a.i./kg, but are considered secondary to maternal toxicity (decreased body weight gain and feed consumption). The No Observable Effect Level (NOEL) for maternal toxicity was 100 mg a.i./kg/day.

Executive summary:

The developmental toxicity of OXEMA was assessed in presumed-pregnant Crl:CD®BR rats. OXEMA was suspended in corn oil and administered orally by gavage on days 6-19 of gestation (day of conception designated as Gestation Day (G) 0) at doses of 0 (control), 25, 100 and 300 mg of a.i./kg/day. All doses were administered at a constant volume of 5 ml/kg. Clinical signs were recorded once daily. Body and feed weights were recorded on G3, 6, 9, 12, 15, 18, and 20. On G20, the dams were euthanized, and the thoracic and abdominal cavities were examined for gross changes. Each intact gravid and non-gravid uterus was weighed, and corpora lutea, implantation sites and early and late resorptions were counted. The number of fetuses per litter was counted and their locations within the uterus recorded. All live fetuses were sexed and weighed individually and examined for external alterations. Alternating live fetuses from each litter were examined for soft tissue alterations using the Staples' Technique. The heads from fetuses receiving soft tissue exam were fixed in Bouin's fixative and examined using the technique of Barrows and Taylor. Fetuses receiving soft tissue exams were discarded after evaluation. Skeletal staining (i.e., using alizarin red S) was performed on all remaining fetuses. The stained

fetuses were examined for skeletal alterations.

Two dams were found dead at 300 mg a.i/kg during the study. These deaths were considered treatment-related. No other mortalities occurred. No clinical signs of toxicity were observed in dams at any dose level. There was no effect on gestation body weight or feed consumption at dose levels up to and including 100 mg/kg. Mean gestation body weight at 300 mg/kg was decreased (5-10%) beginning on G9 through G20. Dams at 300 mg/kg lost weight initially (G6-9) and body weight gain during gestation remained depressed (30%) in females at 300 mg/kg throughout the dosing period (G6-20). A corresponding decrease (76%) in net weight change (i.e., net body weight change – uterine weight) was also noted at this level. There was no effect on gravid uterine weight noted at any dose level. Daily feed consumption was decreased (10-43%) throughout the dosing period (G6-20) in dams at 300 mg/kg. There were no treatment-related necropsy findings in dams at dose levels up to and including 100 mg/kg. Reddened and thickened stomachs were noted in dams at 300 mg/kg.

No treatment-related effects were noted in the number of viable litters, mean numbers of resorptions, live or dead fetuses, or in sex ratio per litter at any dose level. There was no effect on fetal body weight at dose levels up to and including 100 mg/kg. A statistically significant decrease (5%) in combined and male fetal body weight was noted at 300 mg/kg. No treatment-related increases were detected in the type or incidence of external, visceral or skeletal variations or malformations at dose levels up to and including 100 mg/kg. There was an increase (although not statistically significant) in skeletal variations noted in fetuses at 300 mg/kg. These included: reduced ossification of the parietals, supraoccipital and interparietal bones of the skull. While the reduced fetal body weight and the increased incidence of reduced ossification were correlated with and considered secondary to the maternal toxicity noted at this level (i.e., decreased weight gain and feed consumption), a causal relationship can not be definitively established. It is clear that the fetus is not uniquely sensitive. The reduced ossification is considered to be related to the reduced fetal body weight.