o-phenylenediamine

Neurotoxicity

Administrative data

Endpoint:

neurotoxicity: sub-chronic oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

The study was conducted according to the EPA guidelines for neurotoxicity testing and used GLP.

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1992

Report date:

1992

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

EPA OTS 798.6050 (Neurotoxicity Screening Battery)

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: EPA OTS 798.6200 and EPA OTS 798.6400

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

o-phenylenediamine

EC Number:

202-430-6

EC Name:

o-phenylenediamine

Cas Number:

95-54-5

Molecular formula:

C6H8N2

IUPAC Name:

benzene-1,2-diamine

Details on test material:

- Name of test material (as cited in study report): 1,3-Benzenediamine
- Purity: ≥98%.

Test animals

Species:

rat

Strain:

other: Cr1:CD BR

Sex:

male/female

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: methyl cellulose (0.5% w/v)

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: The test substance suspension was prepared daily. Nominal concentrations (pure test substance) of 0 (vehicle), 2, 4, and 8 mg/mL were prepared for administration of 0, 20, 40, and 80 mg/kg, respectively, at a dosage volume of 10 mL/kg. All prepared concentrations were adjusted on the basis of a 98% purity of the test substance.

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

90 days.

Frequency of treatment:

One daily gavage/day

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

20 other: mg/kg (analytical conc.)

Doses / concentrations 2

Dose / conc.:

40 other: mg/kg (analytical conc.)

Doses / concentrations 3

Dose / conc.:

80 other: mg/kg (analytical conc.)

No. of animals per sex per dose:

10 rats/sex/dose.

Examinations

Observations and clinical examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes, at least once daily.

BODY WEIGHT: Yes
- Time schedule for examinations: on the day after arrival, at least twice during the quarantine period, at least twice weekly the first month of dosing, and weekly thereafter, as well as on the days of assessment.

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes, weekly

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: Opthalmological evaluations were conducted initially on all rats received for the study and again at the end of the dosing period, prior to sacrifice.

Neurobehavioural examinations performed and frequency:

A neurobehavioural test battery, consisting of motor activity and a functional observational battery (FOB) assessment, was conducted during the week prior to the dosing period to determine a baseline measurement. These neurobehavioral test batteries were conducted again during weeks 4, 8, and 13 of dosing.

Each rat was evaluated in three "environments": in their home cage, upon removal from their home cage, and in a standard arena. At each evaluation period, the FOB and MA were jointly conducted. The "home cage" and "home cage removal" assessments of the FOB were conducted in the animal room and then the animals were transported to a nearby laboratory where they were tested for MA and evaluated in a standard arena for additional FOB endpoints. Any unusual responses with respect to body position, activity level, coordination, behavior and gait were recorded. In addition, the presence of convulsions/tremors, lacrimation, salivation, piloerection, labored breathing, diarrhea, urination, and vocalization were also recorded. While the rat was in the standard arena, simple assessments of sensory functions were made. Pupillary constriction, forelimb/hindlimb grip strength and hindlimb splay were measured following each MA session.

MOTOR ACTIVITY:
All rats were individually tested in one of eight, nominally identical, automated activity monitors. Group and sex were counterbalanced across the 8 monitors and time.

Sacrifice and (histo)pathology:

After completion of at least 90 days of dosing, the rats were sacrificed by a barbiturate overdose via intraperitoneal injection and underwent in situ whole body perfusions.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Description (incidence and severity):

The 80 mg/kg dose increased or significantly increased the incidence of female rats with persistent or recurrent observations of yellow staining of the perineum, inguen, abdomen and/or underbody. No clinical signs noted in the male rats were attributed to the test substance.

Mortality:

no mortality observed

Description (incidence):

No substance-related deaths occurred. One 40 mg/kg dose group male rat was removed from the study on day 5 due to a non-test substance related injury. One 80 mg/kg dose group male rat had similar observations as well as at least one control animal.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Biological remarkable and/or statistically significant decreases in average body weight gain occurred in the 80 mg/kg dose group of male rats during the 4th, 6th, 9th, and 12th weeks of the dosing period. In female rats, average body weight gain was significantly reduced in the 80 mg/kg dose group during the fourth week of the dosing period. Body weight gain over the entire 13-week dosing period was significantly decreased in the 40 mg/kg dose group male rats, as compared to the control group. No other treatment-related differences in body weight gain occurred. Average body weights were unaffected in male and female rats throughout the 13-week dosing period. Differences were neither biologically remarkable nor statistically significant.

Food efficiency:

effects observed, treatment-related

Description (incidence and severity):

Average feed efficiency (g weight gain/ g feed consumed) in the 80 mg/kg dose group of male rats was statistically reduced the sixth and the thirteenth weeks of the dosing period. In female rats, biologically remarkable and/or statistically significant reductions in feed efficiency occurred in the 80 mg/kg dose group during the 1st, 4th, and 10th weeks of the dosing period. There were no other treatment-related changes in feed efficiency. Average absolute feed consumption values (g) were unaffected in male and female rats throughout the 13-week dosing period. Differences were neither biologically remarkable nor statistically significant.

Behaviour (functional findings):

effects observed, treatment-related

Description (incidence and severity):

The 80 mg/kg dose of the test substance resulted in biologically remarkable and/or statistically significant increases in the incidence of male and female rats with observations of slight palpebral closure. Additionally, the 80 mg/kg dose increased the incidence of male rats with enhanced tail pinch responses and female rats with observations of soiled fur. Forelimb grip strength, hindlimb grip strength and foot splay scores, as well as all other parameters evaluated in the FOB, were unaffected by the test substance.

Neuropathological findings:

no effects observed

Description (incidence and severity):

Neuropathology evaluations did not reveal abnormalities within the nervous system or skeletal muscle. No test substance-related effects on ocular tissue were observed.

Effect levels

Dose descriptor:

NOEL

Effect level:

40 mg/kg bw/day (actual dose received)

Sex:

male/female

Applicant's summary and conclusion

Conclusions:

Neuropathological evaluations did not reveal abnormalities within the nervous system or skeletal muscle. No test substance-related effects on ocular tissue were observed. On the basis of this data, the no-observable effect level (NOEL) for OPD in both male and female rats is 40 mg/kg. With the possible exception of enhanced tail pinch responses in the 80 mg/kg dose group male rats, none of the effects at the 80 mg/kg dose level were considered to be neurotoxic.

Executive summary:

Male and female rats were administered OPD orally via gavage at doses of 0, 20, 40, an d80 mg/kg for a minimum of 90 consecutive days. A neurobehavioral test battery, consisting of motor activity and functional observational battery (FOB) assessments, was conducted the week prior to the onset of the dosing period in order to obtain baseline measurements. This neurobehavioral test battery was conducted again during Weeks 4, 8, and 13 dosing. Following completion of the dosing period, surviving rats were sacrificed and perfused, and neuropathology evaluations were conducted.

 

No substance-related deaths occurred. The 80 mg/kg dose increased or significantly increased the incidence of female rats with persistent or recurrent observations of yellow staining of the perineum, inguen, abdomen and/or underbody. No clinical signs noted in the male rats were attributed to the test substance. 

                                                           

Biological remarkable and/or statistically significant decreases in average body weight gain occurred in the 80 mg/kg dose group of male rats during the 4th, 6th, 9th, and 12th weeks of the dosing period. In female rats, average body weight gain was significantly reduced in the 80 mg/kg dose group during the fourth week of the dosing period. No other treatment-related differences in body weight gain occurred. Average body weights were unaffected in male and female rats throughout the 13-week dosing period. Differences were neither biologically remarkable nor statistically significant.

                                                                                                                       

Average feed efficiency (g weight gain/ g feed consumed) in the 80 mg/kg dose group of male rats was statistically reduced the sixth and the thirteenth weeks of the dosing period. In female rats, biologically remarkable and/or statistically significant reductions in feed efficiency occurred in the 80 mg/kg dose group during the 1st, 4th, and 10th weeks of the dosing period. There were no other treatment-related changes in feed efficiency. Average absolute feed consumption values (g) were unaffected in male and female rats throughout the 13-week dosing period. Differences were neither biologically remarkable nor statistically significant.                    

                                                           

The 80 mg/kg dose of the test substance resulted in biologically remarkable and/or statistically significant increases in the incidence of male and female rats with observations of slight palpebral closure. Additionally, the 80 mg/kg dose increased the incidence of male rats with enhanced tail pinch responses and female rats with observations of soiled fur. Forelimb grip strength, hindlimb grip strength and foot splay scores, as well as all other parameters evaluated in the FOB, were unaffected by the test substance.

                                                                                                                       

Neuropathology evaluations did not reveal abnormalities within the nervous system or skeletal muscle. No test substance-related effects on ocular tissue were observed.

   

On the basis of these data, the no-observable effect level for OPD in both the male and female rats was 40 mg/kg. With possible exception of enhanced tail pinch responses in the 80 mg/kg group male rats, none of the effects seen at the 80 mg/kg dose level were considered to be neurotoxic.