Diethylbenzene

Repeated dose toxicity: other routes

Administrative data

Endpoint:

sub-chronic toxicity: other route

Adequacy of study:

supporting study

Study period:

1991

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Meets generally accepted scientific standards, well-documented and acceptable for assessment.

Data source

Reference

Reference Type:

publication

Title:

Possible Involvement of 1,2-Diacetylbenzene in Diethylbenzene-Induced Neuropathy in Rats

Author:

Gagnaire, F., Ensminger, A., Marignac, B., and De Ceaurriz, J.

Year:

1991

Bibliographic source:

Journal Appl. Tox. 11: 261-268.

Materials and methods

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

1,2-diacetylbenzene

IUPAC Name:

1,2-diacetylbenzene

Details on test material:

IUCLID4 Test substance: A01-03:1,2-Diacetylbenzene (98%) and diethylether (uvasol)

1,2-Diacetylbenzene [DAB] (98%) and diethylether (uvasol) were obtained from Merck-Schuchardt, Darmstadt, Germany.

1,2-Diethylbenzene (95%) was supplied by Aldrich, Steinheim, Germany. Gas chromatography-mass spectrometry showed that 1,2-DEB was free from 1,2-DAB.

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Administration / exposure

Route of administration:

other: ip and oral

Details on exposure:

Experiment A
In experiment A, 34 rats were assigned to two treatment groups (12 rats  each) and one control group (10 rats).  Treated groups were given  intraperitoneally either 10 mg/kg 1,2-diacetylbenzene(DAB), 4 days per  week for 11 weeks, or 20 mg/kg 1,2-DAB, 4 days per week for 6 weeks.   Controls received vehicle (a mixture of saline and 2% acetone) only.                        

Experiment B
In experiment B, four rats were administered orally 165 mg/kg 1,2-DEB in  olive oil, on four consecutive days.  Controls received vehicle (olive  oil) only.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

6 or 11 weeks
Experiment A
In experiment A, 34 rats were assigned to two treatment groups (12 rats  each) and one control group (10 rats).  Treated groups were given  intraperitoneally either 10 mg/kg 1,2-diacetylbenzene(DAB), 4 days per  week for 11 weeks, or 20 mg/kg 1,2-DAB, 4 days per week for 6 weeks.   Controls received vehicle (a mixture of saline and 2% acetone) only.

Experiment B
In experiment B, four rats were administered orally 165 mg/kg 1,2-DEB in  olive oil, on four consecutive days.  Controls received vehicle (olive  oil) only.              

Frequency of treatment:

4 days/week

Experiment A
In experiment A, 34 rats were assigned to two treatment groups (12 rats  each) and one control group (10 rats).  Treated groups were given  intraperitoneally either 10 mg/kg 1,2-diacetylbenzene(DAB), 4 days per  week for 11 weeks, or 20 mg/kg 1,2-DAB, 4 days per week for 6 weeks.   Controls received vehicle (a mixture of saline and 2% acetone) only.

Experiment B
In experiment B, four rats were administered orally 165 mg/kg 1,2-DEB in  olive oil, on four consecutive days.  Controls received vehicle (olive  oil) only.          

Doses / concentrations

Remarks:

Doses / Concentrations:
i.p. - 10 or 20 mg/kg 1,2-DAB; orally - 165 mg/kg

No. of animals per sex per dose:

Experiment A
In experiment A, 34 rats were assigned to two treatment groups (12 rats  each) and one control group (10 rats).  Treated groups were given  intraperitoneally either 10 mg/kg 1,2-diacetylbenzene(DAB), 4 days per  week for 11 weeks, or 20 mg/kg 1,2-DAB, 4 days per week for 6 weeks.   Controls received vehicle (a mixture of saline and 2% acetone) only.

Experiment B
In experiment B, four rats were administered orally 165 mg/kg 1,2-DEB in  olive oil, on four consecutive days.  Controls received vehicle (olive  oil) only.          

Control animals:

yes, concurrent vehicle

Details on study design:

Post-exposure period: 5 weeks

Examinations

Observations and examinations performed and frequency:

Neurophysiological measurements
Neurophysiological measurements were conducted in a room maintained at 25  - 26°C.  The motor conduction velocity (MCV) and sensory conduction  velocity (SCV) of the tail nerve and the amplitude of the sensory action  potential (ASAP) were measured.    

Experiment A
Rats were observed daily, weighed weekly and subjected to  electrophysiological measurements every 2 weeks during the course of  treatment and through the recovery period of 5 weeks. After the recovery  period, they were sacrificed for post-mortem examination.                        

Experiment B
Urine from each animal was collected for 24 h after the end of the  treatment.  The 24-h urine samples then were pooled and stored at -20°C  for further gas chromatography-mass spectrometry analysis.               

               

Statistics:

Differences in mean body weight, MCV, SCV and ASAP between experimental  and control groups were analysed using Students's t-test for independent  data.  Differences were considered to be statistically significant at the  P<0.05 level.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Behaviour (functional findings):

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Details on results:

Rats treated with 10 or 20 mg/kg 1,2-DAB developed hyperactivity after  each injection, with stereotyped behavour (sniffing and rummaging in the  sawdust).  They exhibited a blue discoloration of skin and urine.  Hair  was also discolored at the i.p. injection point.  A general discoloration  of skin appeared between the 3rd and 5th days of treatment.

Significant reduction in weight gain was observed from the 1st week of  treatment in the group treated with 20 mg/kg.  In the high-dose group,  two animals died during the 3rd week of treatment; there were nine, eight  and seven surviving rats at weeks 4, 5, and 6, respectively.  One more  rat died in the 2nd week of the recovery period.  No animal died in the  low-dose group.  One rat died in the control group during the 2nd week  due to a bad injection.  Rats treated with 20 mg/kg 1,2-DAB developed  severe weakness in hind limbs and disturbance in gait from the 4th week  of the experiment. At the 5th week of treatment, four rats showed  evidence of foot drop and muscle atrophy.  The three other rats in this  group showed an awkward gait.  Soon the hind limbs became so weak that  animals crawled.  At the 6th week, rats developed complete paralysis of  the hind limbs and treatment was stopped because of the excessive poor  condition.  During the first week of the excessively poor condition, they  were fed by oral gavage with a nutritive solution.

In the low-dose group, rats exhibited decreased weight gain.  Weakness  developed after 6 weeks of treatment, but no paralysis was seen.

During the recovery period, the 1,2-DAB treated rats regained weight.   Two weeks after the last treatment, the high-dose treated rats became  more mobile although they dragged their hind limbs.  On the 5th week they  were able to stand up but had an awkard gait.  Low dose treated rats,  except for body weight, were indistinguishable from controls at the end  of the recovery period.

At necropsy, internal organs appeared bluish and brain and nerves showed  a blue-grey color.

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

The findings in this study support the hypothesis that the formation of 1,2-diacetylbenzene derivatives contributes to the neurotoxicity of 1,2-DEB.