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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable, well-documented publication and study report which meets basic scientific principles.

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1986

Materials and methods

Test guideline
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Maleic anhydride was supplied by Monsanto Company as white briquettes with a purity of greater than 99%.

Test animals

Species:
rat
Strain:
Sprague-Dawley
Details on test animals or test system and environmental conditions:
Adult CD rats (Charles River Breeding Laboratories, Wilmington, Mass.), approximately 12 weeks of age, were used in the teratology study.
All rats were acclimated to the laboratory for at least 10 days prior to initiating a study. Rats were individually housed, except during mating and lactation, in wire mesh cages or plastic cages with corn-cob bedding. All animals were maintained in environmentally controlled rooms with 12-hr photoperiods and given free access to feed (Purina Rodent Chow, Ralston-Purina, St. Louis, Mo.) and water.

Administration / exposure

Route of administration:
oral: unspecified
Vehicle:
corn oil
Details on exposure:
Briquettes of maleic anhydride were finely ground with a mortar and pestle and suspended in corn oil with the aid of a tissue homogenizer. All doses were prepared daily in corn oil in order to minimize problems with stability. A 1% (w:v) concentration was used to administer all doses.
Analytical verification of doses or concentrations:
not specified
Details on analytical verification of doses or concentrations:
no data
Details on mating procedure:
One male and one female were housed together for mating.
Duration of treatment / exposure:
Day 20 of gestation
Frequency of treatment:
Day 6-15 of gestation
Duration of test:
not specified
Doses / concentrations
Remarks:
Doses / Concentrations:
30, 90, and 140 mg/kg/day
Basis:

No. of animals per sex per dose:
25 mated females/group
Control animals:
yes, concurrent no treatment
Details on study design:
- Dose selection rationale: In a pilot study, conducted to identify doses for the teratology study, three of five and five of five dams died after doses of 192 and 256 mg/kg, respectively, of maleic anhydride.

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
DETAILED CLINICAL OBSERVATIONS: No data
BODY WEIGHT: Yes
FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): No data
POST-MORTEM EXAMINATIONS: No data
- Sacrifice on gestation day 20
- Organs examined: no data
Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
Fetal examinations:
All fetuses were weighed and examined for external abnormalities. Approximately one-third of the fetuses were placed in Bouin's fixative and examined for soft tissue abnormalities (Wilson, 1965). The remaining fetuses were fixed in alcohol, cleared with potassium hydroxide, stained with Alizarin Red S (Dawson, 1926), and examined for skeletal abnormalities.
Statistics:
Statistical analysis. Several different statistical methods were used to compare measurements made on test animals to the corresponding values determined for controls. The methods and the measurements to which they were applied are analyis of variance and Dunnett's test (Steel and Torrie, 1960) for adult body weights, litter size, and pup body weights; Fisher's exact probability test (Siegel, 1956) for mortality and fertility data; Mann-Whit-ney U test (Siegel, 1956) for fetal body weights; and x2 test with Yates' correction or Fisher's exact probability test (Siegel, 1956) for litters with anomalies. In all instances, p < 0.05 was selected as the level of significance.
Indices:
no data
Historical control data:
yes

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:no effects

Details on maternal toxic effects:
The general appearance and behavior of rats were not altered by treatment. While one adult died in each of the experimental groups, the overall survival in these groups was 96% (Table 1). Dams in the experimental groups either failed to gain weight or lost weight between Days 6 and 9 of gestation (Table 1). However, this effect was reversible, and there were no statistically significant effects on body weight at any of the times examined.
Dams from all test groups produced normal-sized litters, and there was no evidence of postimplantation loss.

Effect levels (maternal animals)

Dose descriptor:
NOAEL
Effect level:
140 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:
Compared with concurrent controls, fetal body weights were slightly reduced for all test groups, but the reductions were statistically significant only in the low- and high-dose groups. However, this is not considered to be compound-related, because fetal weights for concurrent control and all treated groups were slightly greater than the values for historical controls.
The malformations and variations observed during the fetal examinations are summarized in Table 2. Malformations were observed in one fetus (one litter) from the control group, two fetuses (two litters) from the low-dose group, and three fetuses (three litters) from the high-dose group. Since each malformation was a single occurrence and the malformations differed among the various groups, there was no evidence of a dose-related increase in any specific malformation. The fetal variations were comparable both in type and frequency in the control and treated groups.

Effect levels (fetuses)

open allclose all
Dose descriptor:
NOAEL
Effect level:
140 mg/kg bw/day
Basis for effect level:
other: teratogenicity
Dose descriptor:
NOAEL
Effect level:
140 mg/kg bw/day
Basis for effect level:
other: fetotoxicity

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Any other information on results incl. tables

 Maleic anhydride (mg/kg/day) 

 

 0 

 30 

 90 

 140 

 Number treated 

 25 

 25 

 25 

 25 

 Pregnant 

 23 

 24 

 20 

 21 

 Alive 

 23 

 23 

 19 

 21 

 Nonpregnant 

 2 

 1 

 5 

 4 

 Alive 

 2 

 1 

 5 

 3 

 Body weight (g) 

 

 

 

 

 Day 0

 242 

 244 

 242 

 243 

 Day 6 

 261 

 264 

 266 

 264 

 Day 9 

 272 

 264 

 264 

 258 

 Day 12 

 293 

 286 

 283 

 282 

 Day 15 

 315 

 302 

 303 

 298 

 Day 20 

 397 

 377 

 385 

 378 

 Implants/dam 

 13.3(14)a

 13.4(14) 

 13.2(13) 

 13.5(14) 

 Viable fetuses/dam 

 12.6(13) 

 12.7(13) 

 12.5(13) 

 12.7(13) 

 Resorptions/dam 

 0.8 (0) 

 0.7(0) 

 0.7(1) 

 0.8 (0) 

 Fetal weight (g) 

 4.0(3.8) 

 3.7(3.8)b

 3.8(3.8) 

 3.7 (3.6)b

" Mean (median).

* Mean significantly different from control. The historical control value for fetal weight was 3.6 g for 1774 fetuses.

 

OBSERVATIONS OF FETUSES FROM RATS TREATED WITH MALEIC ANHYDRIDE DURING GESTATION

 Maleic anhydride (mg/kg/day) 

 

 0 

 30 

 90 

 140 

 Number examined 

 

 

 

 

 Litters 

 23 

 23 

 19 

 21 

 Fetuses 

 

 

 

 

 External 

 289 

 292 

 237 

 267 

 Skeletal 

 189 

 190 

 155 

 174 

 Soft tissue 

 100 

 102 

 82 

 93 

 Malformations 

 

 

 

 

 Short tail 

 — 

 1(1)a

 — 

 — 

 Omphalocele 

 — 

 — 

 — 

1(1)

 Spherical enlargement on ribs 

 1(1) 

 — 

 — 

 — 

 Fused sternebrae 

 — 

1(1)

 — 

 — 

 Bent ribs 

 — 

 — 

 —

1(1)

Multiple anomalies

 — 

 — 

 —

1(1)b

 Total with above malformations 

 1(1) 

 2(2) 

 0(0) 

 3(3) 

 Variations 

 

 

 

 

 Rudimentary 14th rib(s) 

 51(17) 

 62 (20) 

 46(16) 

 37(13) 

 Full 14thrib(s)

 1(1)

 2(2)

 3(3)

 1(1)

27 presacral vertebrae 

 — 

5(4) 

2(1) 

2(2) 

 Sternebrae 5 and/or 6 unossified 

 12(9) 

 16(7) 

 12(6) 

 20(12) 

 7th cervical rib 

 3(2) 

 1(1) 

 1(1) 

 — 

 Misaligned centra 

 — 

 — 

 — 

 1(1) 

 Reduced ossification of skull 

 — 

 1(1) 

 — 

 1(1) 

 Hyoid unossified 

 — 

 5(3) 

 — 

 — 

 Pubis unossified 

 — 

 1(1) 

 — 

 — 

 Renal papillar not developed 

 2(2) 

 — 

 — 

 1(1) 

" Number of fetuses (number of litters).

* Includes malformed humerus, stemoschisis, and ossification defects of the pubis, cervical arches, and skull.

Applicant's summary and conclusion

Conclusions:
There was, however, no maternal NOEL because females at 30 mg/kg failed to gain weight from gestation day 6-9 although this was not statistically significant. The NOAEL for both maternal and developmental toxicity was 140 mg/kg/day.
Executive summary:

The maternal toxicity effects are likely to reflect the toxicity of maleic acid since maleic anhydride is rapidly hydrolyzed to maleic acid in the body, particularly by the oral route of exposure.