Reaction mass of methyl chloroacetate and chloroacetic acid

Neurotoxicity

Administrative data

Endpoint:

neurotoxicity: acute oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The publication provides information on the effects of chloroacetic acid on the blood-brain barrier function. No data on GLP.

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1987

Materials and methods

Principles of method if other than guideline:

Preliminary studies had indicated that mice surviving a toxic dose of monochloroacetic acid may develop rigid clasping of the front paws as early as 24 hr after treatment. The present investigation was undertaken to further characterize this rigidity, and to study its association with monochloroacetic acid-induced blood-brain barrier damage in mice.
Male Swiss Webster mice were used in the test. The substance was orally administered with a constant volume (0.2 mL/26 g). The doses tested were 320 and 380 mg/kg bw. Immediately following the treatment the animals were observed for a period between 48 hours and 8 weeks.

GLP compliance:

not specified

Limit test:

no

Test material

Reference

Name:

Unnamed

Type:

Constituent

Details on test material:

- Name of test material (as cited in study report): Monochloroacetic acid
- Analytical purity: approx 99%

Test animals

Species:

mouse

Strain:

Swiss Webster

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Perfection Breeders (Douglassville, PA).
- Weight at study initiation: 25- 30 g
- Housing: Animals were housed 20 to a cage in polypropylene "shoebox" cages with zinc-plated wirebar lids and Beta-Chip Hardwood Laboratory Bedding (Northeastern Products Corp., Warrensburg, NY).
- Diet (e.g. ad libitum): Purina Rodent Chow (Ralston Purina Co., St. Louis, MO); ad libitum.
- Water (e.g. ad libitum): tap water; ad libitum.
- Acclimation period: At least 1 week.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ºC
- Humidity (%): 55 %
- Photoperiod: 12 hrs dark / 12 hrs light.

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

For oral administration, monochloroacetic acid was dissolved in deionized water, and a constant volume of 0.2 mL/26 g was given.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

A single oral exposure

Frequency of treatment:

A single exposure

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
320 mg/kg bw
Basis:
nominal conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
380 mg/kg bw
Basis:
nominal conc.

No. of animals per sex per dose:

8-10 male animals per group

Control animals:

yes, concurrent vehicle

Examinations

Sacrifice and (histo)pathology:

Histological examination of brain tissue: Control mice, as well as 48-hr and 2-, 5-, and 8-week survivors from the acute toxicity studies exhibiting varying degrees of front paw rigidity were anesthetized with methohexital sodium, and perfused via the left ventricle with 20 mL of 10% phosphate-buffered formalin. Brains were removed and fixed in 10% phosphate-buffered formalin for 3 days, then transferred to 70% ethanol for storage. The tissues were later dehydrated, cleared, embedded in paraffin, and 6-µm-thick sections were cut on a rotary microtorne using standard histological techniques (Luna, 1968). Midsagittal sections were utilized so that all areas of the brain could be viewed on one slide. Slides were prepared in triplicate and stained with hematoxylin and eosin for a general cytological stain (Luna, 1968), Luxol Fast Blue G with a eresyl fast violet counterstain to outline the myelin sheath (La Bossiere, 1976), and the Bodian stain for nerve fibers.

Statistics:

For experiments with only control and one treatment group, the means of the groups were compared using the Student's t test and a 5% significance level. For experiments with several treatment groups, a one-way analysis of variance (ANOVA) was used to test for differences among treatment groups. If the F value was significant (p < 0.05), Student's t test was employed to compare the means of the groups.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

not specified

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Clinical biochemistry findings:

not examined

Behaviour (functional findings):

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Neuropathological findings:

effects observed, treatment-related

Details on results:

No significant lesions were observed in the control mice at the light microscopic level. Treated rats, however, had lesions. Two 48-hr brains showed pyknosis of Purkinje cell nuclei, and bright red staining of the cell body was observed in two of the three 48-hr brains. No other lesions were observed. Two weeks following MCA exposure the Purkinje cells were fewer in number as seen by discontinuities in the Purkinje cell layer. Two weeks after MCA there were also more Purkinje cells with damaged nuclei and bright red staining of the perikaryon. RBCs outside capillaries were seen in the molecular layer of the cerebellum. A progression of the damage was seen in MCA-treated animals 5 weeks post-treatment, with fewer Purkinje cells lining the granular
cell layer and fewer pyknotic nuclei, suggesting that all the damaged cells have undergone necrosis and have been removed. RBCs were still present at these later time points and appeared to be undergoing necrosis. This indicated that the presence of the RBCs outside the capilIary was not an artifact caused by perfusion of the brains and dislodging of the RBCS.
Although the pathological changes were first seen almost exclusively in the cerebellum, further examination of these brains revealed damage in other areas. After 2 weeks the brain of one mouse exhibited a necrotic focus in the pons. Pyknotic nuclei were observed in treated animals in the brainstem, hippocampus, and cerebral cortex at 2 and 5 weeks after treatment. There was also an apparent increase in vacuoles in the brains of MCA-treated animals, but it cannot be determined if this was treatment-related or an artifact caused by perfusion of the brains and fixation ofthe tissues.

Effect levels

Dose descriptor:

NOAEL

Sex:

male

Basis for effect level:

other: overall effects

Remarks on result:

not determinable

Remarks:

no NOAEL identified

Any other information on results incl. tables

Monochloroacetic acid causes front paw rigidity in 10% of mice surviving a single oral toxic dose (320 -380 mg/kg bw). Mice exhibiting front paw rigidity were killed at various times after the treatment and their brains were prepared for histological examination. As early as 48 hr post-treatment, RBCs were found outside capillaries in several brain regions, especially the cerebellum. At time points up to 8 weeks after treatment, extracapillary RBCs were seen to be undergoing lysis, and there was loss of cerebellar Purkinje cells.

Applicant's summary and conclusion

Conclusions:

Monochloroacetic acid causes front paw rigidity in 10% of mice surviving a single oral toxic dose (320 -380 mg/kg bw). Mice exhibiting front paw rigidity were killed at various times after the treatment and their brains were prepared for histological examination. As early as 48 hr post-treatment, RBCs were found outside capillaries in several brain regions, especially the cerebellum. At time points up to 8 weeks after treatment, extracapillary RBCs were seen to be undergoing lysis, and there was loss of cerebellar Purkinje cells.

Executive summary:

Preliminary studies had indicated that mice surviving a toxic dose of monochloroacetic acid may develop rigid clasping of the front paws as early as 24 hr after treatment. The present investigation was undertaken to further characterize this rigidity, and to study its association with monochloroacetic acid-induced blood-brain barrier damage in mice.

Male Swiss Webster mice were used in the test. The substance was orally administered with a constant volume (0.2 mL/26 g). The doses tested were 320 and 380 mg/kg bw. Immediately following the treatment the animals were observed for a period between 48 hours and 8 weeks.

Monochloroacetic acid causes front paw rigidity in 10% of mice surviving a single oral toxic dose (320 -380 mg/kg bw). Mice exhibiting front paw rigidity were killed at various times after the treatment and their brains were prepared for histological examination. As early as 48 hr post-treatment, RBCs were found outside capillaries in several brain regions, especially the cerebellum. At time points up to 8 weeks after treatment, extracapillary RBCs were seen to be undergoing lysis, and there was loss of cerebellar Purkinje cells.