Tricarbonyl(methylcyclopentadienyl)manganese

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

February 1979-August 1979

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1979

Report date:

1979

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

yes

Remarks:

The purity of the substance is not mentioned

GLP compliance:

yes

Remarks:

The report indicates compliance with GLP guidelines.

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Tricarbonyl(methylcyclopentadienyl)manganese

EC Number:

235-166-5

EC Name:

Tricarbonyl(methylcyclopentadienyl)manganese

Cas Number:

12108-13-3

Molecular formula:

C9H7MnO3

IUPAC Name:

tricarbonyl(methyl-η5-cyclopentadienyl)manganese

Details on test material:

- Name of test material (as cited in study report): mmt
- Physical state: Liquid

Please refer to section 13 "Purity statement".

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc., Portage, Michigan)
- Age at study initiation: 15 weeks
- Weight at study initiation: 220 to 280 g
- Fasting period before study: No
- Housing: Individually housed except during mating in suspended wire mesh cages
- Diet (e.g. ad libitum): Purina Rodent Laboratory Chow #5001 ad. libitum
- Water (e.g. ad libitum): ad. libitum
- Acclimation period: 5 weeks


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 to 24
- Humidity (%): 45 +/- 10
- Air changes (per hr): -
- Photoperiod (hrs dark / hrs light): 12 hrs dark/12 hrs light


IN-LIFE DATES: The administration of the test compound was until the day 15 of gestation, and the rats were sacrificed at gestation day 20.

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: Dosage volumes administrated were 7.14 ml/kg, 7.50 ml/kg, 7.56 ml/kg and 6.72 ml/kg. Individual dosages were determined from individual body weight.



VEHICLE
The vehicle was prepared, assayed and shipped to the research laboratory.

Analytical verification of doses or concentrations:

no

Details on analytical verification of doses or concentrations:

The solutions of the test compound in the vehicle were prepared by the sponsor. No verification of the test concentrations was performed.

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1:1
- Further matings after two unsuccessful attempts: N.A.
- Verification of same strain and source of both sexes: N.A.
- Proof of pregnancy: copulatory plug

Duration of treatment / exposure:

From gestation day 6 to gestation day 15 (total of 9 days of treatment)

Frequency of treatment:

Single daily dose.

Duration of test:

20 days.

No. of animals per sex per dose:

Vehicle control-25 Female Rats
2.0 mg/kg/day-25 Female Rats
4.5 mg/kg/day-25 Female Rats
6.5 mg/kg/day-25 Female Rats
9.0 mg/kg/day-25 Female Rats

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: A pilot study was conducted preceeding this study to determine the appropriate high-dose levels for a teratology study.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: No specified
- Cage side observations checked in table [No.?] were included. No

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: No

BODY WEIGHT: Yes
- Time schedule for examinations: No
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: Yes

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 20
- Organs examined: Uterus and liver

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: 1/3 per litter
- Skeletal examinations: Yes: 2/3 per litter

Statistics:

Incidence of fetuses and litters with malformations were compared by the Wilcoxon test, as modified by Haseman and Hoel, to judge statiscal significance of differences.
Incidence on maternal deaths, pregnant dams and early resorptions and postimplatation loss were compared using the Chi-square test criterion with Yates correction for 2x2 contingency tables and/or Fisher's exact probability test as described by Siegel to judge significance of differences.
Maternal body weights, maternal liver weights, fetal body weights abd fetal crown-rump lengths were compared by analyses of variance (1-way classification) and t-test described by Steel and Torrie using Dunnets multiple comparison table.

Indices:

All statistical analyses compared the treatment groups to the control group with the level of significance at p<0.05

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
Maternal toxicity due to treatment with mmt was evident at the 9.0 mg/kg/day dosage level as an increase in matting and staining of the anogenital haircoat and a mean maternal weight loss early in the treatment period which was statistically significant in gestation day 9.

Effect levels (maternal animals)

1

Key result

Dose descriptor:

NOAEL

Effect level:

6.5 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

2

Key result

Dose descriptor:

NOAEL

Effect level:

9 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

other: developmental toxicity

Maternal abnormalities

Key result

Abnormalities:

effects observed, non-treatment-related

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
A slight reduction in mean fetal body weights were seen. An increase in the incidence of malformations was noted at all of the mmt dosage levels, exclusively due to the presence of bent ribs when compared with the control group. Bent ribs are not uncommon finding in this strain of rats based on historical data, therefore this effect was not considered a malformation and when present in the exclusion of other malformations is not considered a teratogenic response.

Effect levels (fetuses)

Key result

Dose descriptor:

NOAEL

Effect level:

6.5 mg/kg bw/day (nominal)

Based on:

test mat.

Remarks on result:

not determinable due to absence of adverse toxic effects

Fetal abnormalities

Key result

Abnormalities:

no effects observed

Overall developmental toxicity

Key result

Developmental effects observed:

no

Lowest effective dose / conc.:

9 mg/kg bw/day (nominal)

Treatment related:

no

Any other information on results incl. tables

Maternal observations

1. Appearance and Behavior

There were no biologically meaningful differences in appearance and behaviour attributable to treatment with mmt in the 2.0, 4.5 or 6.5 mg/kg/day dosage groups when compared to the control group. Survival in these three dosage groups and the control group was 100%. A subcutaneous mass in thoracic area was observed in one rat in the 4.5 mg/kg/day dosage group at cesarean section. Upon histological examination, this mass was found to be a mammary adenocarcinoma. This mass was not considered to be a treatment-related effect, as it was located only 14-days after the initiation of test article administration.

A slight increase in matting and staining of the anogenital haircoat was noted in the 9.0 mg/kg/day dosage group when compared to the control group. One rat in this dosage group died on gestation day 11. At necropsy, death was attributed to pneumonia.

There was no statistically significant differences in the incidence of maternal deaths or pregnant dams in any of the mmt treated groups when compared to the control groups.

 

2. Body Weights

A very slight reduction in mean maternal body weight gain was noted from days 12 through 20 of gestation in the 2.0 mg/kg/day dosage groups and from days 6 though 20 of gestation in the 4.5 mg/kg/day dosage group when compared to the control group. This resulted in a slight reduction in mean weight gain over the entire gestation period in these two treatment groups when compared to the control group. A moderate reduction in mean weight gain from days 6 through 9 of gestation in the 6.5 mg/kg/day dosage group and a mean weight loss during this interval, accompanied by a statistically significant reduction in mean maternal body weight on gestation day 9, in the 9.0 mg/kg/day dosage group were noted when compared to the control group. This resulted in moderate reduction in mean maternal body weight gain over the entire gestation period in both of these treatment groups when compared to the control group. With the exception of gestation day 9 in the 9.0 mg/kg/day dosage group, all other mean maternal body weights for the treatment groups were not statistically significant when compared to the control group.

There were no statistically significant or biologically meaningful differences in mean maternal liver weights in any of the mmt treated groups when compared to the control group.

 

3. Caesarean Section Observations

No statistically significant differences in the mean number of early resorptions, post-implantation loss or mean fetal crown-rump lengths were noted in any of the mmt treated groups when compared to the control group. There were no biologically meaningful differences in the mean number of viable fetuses, early resorptions, post-implantation loss, total implantations, corpora lutea or the fetal sex distribution, mean fetal crown-rump length or mean maternal liver weights in any of the treatment groups when compared to the control group.

A slight increase in the mean number of early resorptions and post-implantation loss, a corresponding slight decrease in the mean number of viable foetuses and also a slight decrease in the mean number of total implantations were noted in all of the mmt treated groups when compared to the control group. However, these differences were not considered to be treatment-related, as no dose-related patterns were evident. A slight reduction in mean fetal crown-rump length and a statistically significant decrease in mean fetal body weight were noted in the 6.5 mg/kg/day dosage group. The mean fetal crown-rump length in the 9.0 mg/kg/day dosage group, however, was equal to that in the control group. A slight decrease in mean fetal body weight was noted in all of the mmt treated groups when compared to the control group.

 

Fetal morphological observations

A slight, though not statistically significant, increase in the incidence of fetuses and litters with malformations in the 2.0, 4.5 and 6.5 mg/kg/day dosage groups, and a statistically significant increase in the 9.0 mg/kg/day dosage group were noted when compared to the control group. These increases were deemed to be due to the presence of bent ribs in the mmt treatement groups, which were not dose-dependent increases. No bent ribs were observed in the control group.

Applicant's summary and conclusion

Conclusions:

mmt is not teratogenic at the tested doses, therefore the developmental NOAEL is established as 9.0 mg/kg/day while the NOAEL for maternal toxicity is established at 6.5 mg/kg/day.   

Executive summary:

In a developmental toxicity study performed similar to OECD 422, mmt was administered by oral gavage to 25 females Sprague-Dawley rats at doses of 2.0, 4.5, 6.5 and 9/0 mg/kg/day in corn oil from day 6 through data 15 of gestation.

Maternal toxicity due to treatment with mmt was evident in the 9.0 mg/kg/day dosage level as an increase in matting and staining of the anogenital haircoat and a mean maternal weight loss early in the treatment period which was statistically significant on gestation day 0. A slight reduction in mean fetal body weights and a slight to moderate reduction in mean maternal body weight over the entire gestation period were noted in all of the mmt treatment levels.

An increase in the incidence of malformations was noted at all of the mmt dosage levels. This was exclusively due to the presence of bent ribs at all dosage levels when compared to the control group, however no dose-dependent increase were observed. Bent ribs are not an uncommon finding in this strain of rats based on the historic control data in this laboratory. Therefore bent ribs were not thought to be a malformation in the usual sense and when present with the exclusion of other malformations, as demonstrated in this study, was not considered a teratogenic response. mmt is not teratogenic at the tested doses, therefore the developmental NOAEL is established as 9.0 mg/kg/day while the NOAEL for maternal toxicity is esablished at 6.5 mg/kg/day.