Methylamine

Developmental toxicity / teratogenicity

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: The route of exposure (i.p.) is not standard. Beside that an acceptable, well-documented publication which meets basic scientific principles, test substance used is methylamine hydrochloride

Data source

Reference

Reference Type:

publication

Title:

Developmental toxicity of methylamines in mice

Author:

Guest, I. and Varma, D.

Year:

1991

Bibliographic source:

Journal of Toxicology and Environmental Health 32: 319-330

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Principles of method if other than guideline:

Exploration if chronic administration of methylamines can cause reproductive toxicity using pregnant CD-1mice and mouse embryos in culture as experimental models.

GLP compliance:

not specified

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Methylammonium chloride

EC Number:

209-795-0

EC Name:

Methylammonium chloride

Cas Number:

593-51-1

Molecular formula:

CH5N.ClH

IUPAC Name:

methanaminium chloride

Details on test material:

CAS 593-51-1 (methylamine hydrochloride), purity not specified

Test animals

Species:

mouse

Strain:

CD-1

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, St. Constant, Quebec
- Weight at study initiation: 20-25 g
- Housing: Plexiglas cages with heat-treated wood chip bedding
- Diet (e.g. ad libitum): laboratory mouse chow pellets ad libitum
-Water (e.g. ad libitum): ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22-25°C
- Humidity (%):50-70%
- Photoperiod (hrs dark / hrs light): 12 / 12

Administration / exposure

Route of administration:

intraperitoneal

Vehicle:

other: 0.9% saline

Details on exposure:

intraperitoneal injections, once daily between 08:00 and 09:00 a.m.

Details on analytical verification of doses or concentrations:

no data

Details on mating procedure:

mice bought already mated

Duration of treatment / exposure:

day 1-17 of gestation

Frequency of treatment:

daily

Duration of test:

until day 18 of gestation

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

8 mg/kg bw/day (nominal)

Remarks:

= 0.25 mmol/kg bw

Doses / concentrations 2

Dose / conc.:

31 mg/kg bw/day (nominal)

Remarks:

= 1 mmol/kg bw

Doses / concentrations 3

Dose / conc.:

78 mg/kg bw/day (nominal)

Remarks:

= 2.5 mmol/kg bw

Doses / concentrations 4

Dose / conc.:

155 mg/kg bw/day (nominal)

Remarks:

= 5.0 mmol/kg bw

No. of animals per sex per dose:

5 - 11

Control animals:

yes, concurrent vehicle

Details on study design:

- Six to eight pregnant mice were admininstered 0, 8, 31, 78, and 155 mg/kg bw methylamine by ip injection from day 1 to 17 after mating
- Results of untreated controls of three parallel experiments (n=29) were pooled

Examinations

Maternal examinations:

- Maternal and fetal body weight, mortality, resorptions, litter size, and placental weight were recorded in the in-vivo part of the study

Ovaries and uterine content:

- Examination of uterine content: placental weight, resorptions, litter size
- Examination for obvious sign of implantations (uteri were stained in 10 % ammonium sulfide solution to identify implantation sites)

Fetal examinations:

- Examination of fetuses: viability, body weight, visceral and skeletal examination
pubs weight for each female were calculated by dividing the sum of body weights of all live pups in a litter by the number of live pubs in the litter
mean pub weight for each treatment group was based on sum of mean pup weight for each female divided by the number of females in the group
fetuses were randomly placed either in Bouin solution for visceral examination by the freehand razor sectioning technique or in 95 % ethanol for the skeletal examination by an alizarin red S staining technique.

Statistics:

- Statistical evaluation employed Student's t-test and Bonferroni test (multiple means)

Indices:

no data

Historical control data:

no data

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
- Methylamine hydrochloride did not produce maternal toxicity at concentrations up to 2.5 mmol/kg
- For evaluation the results of untreated controls of three parallel experiments (n=29) were pooled
- No dam died from methylamine hydrochloride treatment and maternal body weight development was within the range if the untreated control group
- No significant differences between control and treated animals were observed concerning fetal body weight, mortality, resorptions , litter size, or placental weight

Effect levels (maternal animals)

Dose descriptor:

NOAEL

Effect level:

155 mg/kg bw/day

Basis for effect level:

other: no effects observed

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
- Methylamine hydrochloride did not have any significant effect on pregnancy outcome.
- Number of resorbed and dead fetuses were equally distributed across all doses of MMA hydrochloride.
- none of the amines (MMA, DMA, TMA) caused a significant increase in external, internal organ, or skeletal abnormalities.
- all three methylamines possess teratogenic potential in varying degrees.
- decrease of DNA, RNA, and protein after treatment of embryos with methylamines.

Effect levels (fetuses)

Dose descriptor:

NOAEL

Effect level:

155 mg/kg bw/day

Basis for effect level:

other: no effects observed

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

In vitro studies: all three methylamines produced concentration-dependent decreases in yolk-sac diameter, crown-rump length, head length, and fetal survival; developmental score and somite number also exhibited a similar concentration-dependent decrease.

The effect of all the three methylamines was more marked on the head length than on crown-rump length and yolk-sac diameter.

the external appearance of embryos was not affected by low concentrations of methylamines. At higher concentrations (> 0.5 mM), there appeared to be a dispropotionate retardation in forelimb and branchial bar development relative to the development of other organs. All embryos were dorsally convex at 1 mM MMA HCl or DMA HCl.

The development of hearts was unaffected at concentrations up to 1 mM of all 3 methylamines and neuropores closed well up to concentrations of 0.75 mM.

All three methylamines produced concentration-dependent decreases in embryo RNA, DNA and proteins; the realtive order of toxicity was the same as in vivo, namely TMA> DMA > MMA.

Applicant's summary and conclusion

Conclusions:

The NOAEL for maternal and developmental toxicity, including teratogenicity, was 155 mg/kg bw Methylammonium chloride based on the absence of any adverse findings at this dose.

Executive summary:

Reproductive toxicity

In a toxicity study in mice no effect of intraperitoneal monomethylamine hydrochloride administration (from day 1 to 17 of gestation) on body weights and food consumption of the females and on organ weights were observed up to 155 mg/kg bw. From the above, it was considered that reproductive/developmental toxicity NOEL is 155 mg/kg bw/day for Methylammonium chloride for female mice. 

Developmental toxicity

A study performed by Guest et al. in 1991, dealt with the investigation of maternal or fetal effects after administration of Methylammonium chloride via intraperitoneal injection. The numbers of resorbed and dead fetuses were equally distributed across all doses of Methylammonium chloride, and, therefore, are considered not to be treatment related. None of the amines (MMA, DMA, TMA) caused a significant increase in external, internal organ, or skeletal abnormalities, but all three possess a teratogenic potential in varying degrees in in vitro experiments on mouse embryos. Monomethylamine hydrochloride did not exert any fetal effects at the highest dose level tested. In vitro, all three methylamines produced concentration-dependent decreases in yolk-sac diameter, crown-rump length, head length, and fetal survival; developmental score and somite number also exhibited a similar concentration-dependent decrease. The external appearance of the embryos was not affected by low concentrations of methylamines, but at higher concentrations (> 0,5 mM), there appeared a disproportionate retardation in the forelimb and branchial bar development relative to the development of other organs. So, Methylammonium chloride inhibits the development of mouse embryos in culture.