4-methylpentan-2-one oxime

Acute Toxicity: oral

Administrative data

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23 October 1989 - 18 October 1991

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1991

Report date:

1991

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 420 (Acute Oral Toxicity - Fixed Dose Method)

Deviations:

no

GLP compliance:

yes

Test type:

fixed dose procedure

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

4-methylpentan-2-one oxime

EC Number:

203-298-2

EC Name:

4-methylpentan-2-one oxime

Cas Number:

105-44-2

Molecular formula:

C6H13NO

IUPAC Name:

4-methylpentan-2-one oxime

Test material form:

liquid

Specific details on test material used for the study:

- Test material: MIBKO (199-89A)
- Batch number: 37905-27-4
- CAS number: 105-44-2
- Physical state: clear liquid
- Purity (active ingredient) : 100%
- other: density: 0.88; flash point: 173 °F; pH 6; solubility: 0.9% in water; boiling point: 94°C
- Storage conditions: temperature monitored room 65°-85°F; store in well ventilated area
- Stability in vehicle: no data

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: On the day of administration, the test item was admistrated undiluted with dose volume adjustùent to achiece the desired tretment levels.
- No correction factor was used in this study.

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source : Charles River Laboratories (CRL), Portage, MI ( or other CRL facilities)
- Sex : Male and Female
- Age : Young adult (approximately 9-12 weeks old at study initiation). Females were nulliparous and nonpregnant
- Weight (-1day) : Males: Approximately 250-360 grams
Females: Approximately 200-270 grams
- Fasting period before study: No
- Housing: One per cage in suspended stainless steel wire mesh bottom cage from day -7 through study termination.
- Water: ad libitum, Municipal water (deionized)
- Diet: ad libitum, RMH 1000 Agway Feed
- Acclimation period: At least 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 64-79°F
- Humidity (%): 40-70%
- Photoperiod (hrs dark / hrs light): 12h/12h

IN-LIFE DATES: From: 23 October 1989 To: 06 November 1989

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

VEHICLE
The test article was administered undiluted with dose volume adjustment to achieve the desired treatment levels.

MAXIMUM DOSE VOLUME APPLIED: 1.5 mL/kg

Doses:

MAIN STUDY GROUPS
Group 1 (Control): 1.50 ml/kg of distilled water
Group 2: 0.15 ml/kg MIBKO (199-89A)
Group 3: 0.75 ml/kg MIBKO (199-89A)
Group 4: 1.50 ml/kg MIBKO (199-89A)

SATELLITE GROUPS
Group 1 (control) : 1.50 of distilled water
Group 2 : 0.15 ml/kg MIBKO (199-89A)
Group 3 : 1.50 ml/kg MIBKO (199-89A)

No. of animals per sex per dose:

For both the Main group and the Satellite group, 5 males and 5 females per dose level.

Control animals:

yes

Remarks:

5 males and 5 females

Details on study design:

MAIN STUDY GROUP
- Duration of observation period following administration: 14 days
- Frequency of observations:
*Clinical signs: three times on day 0 and once daily thereafter from day 1 through day 14.
*Body weight: determined on day 0, 1, 4, 7, 11, and 14.
*Neurotoxicological effects (Modified Irwin Screen): evaluated on day 0, 7, 14.
*Hematological effects : Blood samples were taken on day 14
*Necropsy performed: Yes, on all animals
- animals were sacrificed at the end of the two week study period and gross necropsy examination performed
- Fresh organ weights were obtained for the heart, kidneys, liver, lungs, spleen and testes.
- Selected tissues and organs were collected from each animal and fixed in 10% neutral buffered formalin. Tissue sections of femoral bone marrow, spleen, liver, thymus and testes were subsequently prepared (H&E stained tissue sections) and examined microscopically
- In addition to the above, a bone marrow smear was prepared for each animal at necropsy (femoral bone marrow; Wright-Giemsa stain). These slides were supplied to the examining Pathologist to aid in evaluation of femoral bone marrow tissue sections.

SATELLITE GROUPS
The satellite animals were administered the control (distilled water) or test material in the same manner as main study animals. These animals, however, were utilized only for blood sample collection on the day following dosing and were then sacrificed and discarded. Blood samples from these animals were evaluated for hematological variables which included methemoglobin level.

Statistics:

Body weight, weight gain (cumulative from day 0), organ weight, organ/body weight ratios adn hematology data will be analyzed statistically on a VAX 11/730 computer. Absolute body weight at each measurement interval, cumulative body weight gain from day 0, organ weights, organ/body weight ratios and hematology data will be analyzed using Analysis of Variance (ANOVA) with control to treatment group comparisons performed using dunnett's test. Prior to employing ANOVA, Bartlett's test will be performed to assure that the data are parametric. If a nonparametric procedure is needed, the Kruskal-Wallis test will be used and if differences are indicated, a Mann-whitney U Test will be utilized for control to treatment group comparisons. For all tests, a minimum significance level of 5% will be employed. All statistical evaluations will be two-tailed tests.

Results and discussion

Effect levels

Effect levels 1

Key result

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 1.5 mL/kg bw

Based on:

test mat.

Remarks on result:

not determinable due to absence of adverse toxic effects

Effect levels 2

Sex:

male

Dose descriptor:

other: NOEL

Remarks on result:

other: no NOEL established for males due to the occurence of treatment-related histopathological effect, also in low dose males

Effect levels 3

Sex:

female

Dose descriptor:

other: NOEL

Effect level:

0.15 mL/kg bw

Based on:

test mat.

Mortality:

All main study animals survived to terminal sacrifice on study day 14.
One satellite animal (Female, Group 3; 1.50 ml/kg) was found dead prior to blood sample collection on day 1. No other deaths occurred.

Clinical signs:

other: No significant clinical signs were observed in control animals or animals receiving 0.15 ml/kg MIBKO (199-89A). At the 0.75 and 1.50 ml/kg levels, abnormal signs were observed during the first two days of the study (primarily on day 0). The clinical sign

Gross pathology:

Gross internal abnormalities were limited to diverticulum of the jejunum in one control animal, enlarged cervical lymph node in one mid-dose animal, and mottled spleen in one high-dose animal

Other findings:

NEUROTOXICITY
No abnormalities were detected in the control or low-dose animals during neurotoxicity screening.
Various abnormalities were noted in the mid-dose animals (day 0) and high-dose animals (days 0 and 1).
The most notable effects occurred on day 0 and included impaired mobility (ataxia or prostration); lacrimation; negative or absent response to toe and/or tail pinch; abnormal limb tone with lack of resistance during limb rotation; weak body tone; absent righting reflex; absent startle response; dilated or constricted pupils, abnormal pupil response, abnormal body posture, visual placing absent, grasp response absent, and spatial locomotion restricted.
The incidence of these changes was more pronounced in the high-dose animals but the signs were reversible and no effect were observed on day 7. There was no apparent difference in the overall severity of the above effects between males and females. No abnormalities were noted in the mid-dose animals at the subsequent neurotoxicity screening intervals. Similarly, the signs observed in high dose animals were reversible; no effects were observed at this level at the day 7 screening interval.

HEMATOLOGY
Anemia was evident in mid and high dose males and to a lesser extent in females. This was accompanied by reticulocytosis indicating the anemaia was stimulating a compensatory response in the bone marrow.
Satellite Groups:
Statistically significant difference to the control group included:
- a lower MCHC value in males treated with a dose of 1.50 ml/kg
- an increase in polychromatophilia, poikilocytosis and anisocytosis in the 0.15 and 1.50 ml/kg males.
- a possible slight increase in methemoglobin level was seen in the 1.50 ml/kg males.
- an increase in polychromatophilia in the 1.50 ml/kg females.
- increased methemoglobin and decreased reticulocytes in the 0.15 and 1.5 ml/kg in females
- increased MCH and MCHC levels in 0.15 ml/kg females

Although statistically significant all of the above differences were relatively minor.

Main study group
Statistically significant difference to the control group included:
- an increased reticulocyte count and decreased erythrocyte count, hemoglobin concentration and hematocrit in high-dose males
- an increased MCV and decreased MCHC in high-dose females
- an increased reticulocyte count in mid- and high-dose females
- a slight decrease in erythrocyte count of the mid- and high-dose females

In both high-dose males and females, a possible increase in the occurrence of polychromatophilia was noted. If the occurrence of this finding was combined for both sexes, the resulting incidence in control, low-, mid- and high-dose animals was 1/10, 0/10, 2/10, and 8/10, respectively.

ORGAN WEIGHTS
Absolute and relative spleen weight of the high-dose males was statistically increased as compared to control values. An apparently incidental statistical decrease in relative liver weight was noted in 0.15 ml/kg females.

HISTOPATHOLOGY
Test material-related changes were observed in the tissues of males and females of the 0.75 and 1.50 ml/kg groups, and in males of the 0.1.5 ml/kg group;
These changes included minimal to mild increased erythropoiesis in the spleen and bone marrow; minimal or mild hemosiderosis and minimal to marked congestion in the spleen; and minimal erythropoiesis in the liver.
The liver, spleen and bone marrow changes were observed at all three dose levels for males, and mid- and high-dose levels for females. Test material-related changes generally occurred in a dose-related incidence and severity. The noted microscopic changes were considered to be a physiologic response to a probable direct test material effect upon erythrocytes.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

The acute oral LD50 of MIBKO (199-89A) in rats was determined to be greater than 1.50 ml/kg body weight (the highest dose tested) for both males and females.

Executive summary:

MIBKO (Sample No. 199 -89A) was evaluated for its acute oral toxicity in rats. Animals received a single oral dose of MIBKO at levels of 0.15, 0.75 or 1.5 mL/kg. Control animals were dosed with distilled water. Following dosing, the animals were observed for a period of 14 days for signs of toxicity. Blood samples were taken from selected animals 24 hours after dosing for methemoglobin analyses. Blood samples were taken from the remaining rats on Day 14 of the study for a complete hematology evaluation. The animals were sacrificed at the end of the two week study period and gross necropsy performed. Organ weights were obtained and selected tissues examined microscopically.

No deaths occurred in the main study animals. Therefore, the acute oral LD50 for MIBKO in rats was considered to be greater than 1.5 mL/kg, the highest dose level tested. Exposure to MIBKO caused a transient narcosis at the mid and high dose levels which was no longer evident 48 hours after dosing. Anemia was evident in mid and high dose males and to a lesser extent in females. This was accompanied by reticulocytosis indicating the anemia was stimulating a compensatory response in the bone marrow. Splenomegaly was apparent in the high dose males. Microscopic examination of the spleen revealed extramedullary hematopoiesus and hemosiderosis in low, mid and high dose males and in mid and high dose females which would be consistent with a hemolytic anemia. Based on the results of the microscopic examination, 0.15 mL/kg was considered to be a NOEL for females. A NOEL was not established for male rats.

The findings of anemia and narcosis observed for MIBKO in this study suggest toxicity similar to that previously observed for other oximes.