Registration Dossier

Toxicological information

Repeated dose toxicity: oral

Currently viewing:

Administrative data

Endpoint:
short-term repeated dose toxicity: oral
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1986
Report Date:
1986

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity in Rodents)
GLP compliance:
yes (incl. certificate)
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
CHEMICAL NAME: m-Diisopropylbenzene
HAEL NO.: 85-0077
EK ACC. NO.: 070726
SRID OR LOT NO.: X-17111-47A
EXPERIMENT NO.: 85-0077G2
PURITY ANALYSIS: High pressureliquid chromatography analysis was conducted by the Chemical Quality Services Organization. The sample contained one major peak, m-diisopropylbenzene, which comprised 95.2% of the sample. A minor peak, which comprised 4.3% of the sample, was not identified.

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
Animals: Five male and five female rats (CRL:COBS CD(SD)BR) from CharlesRiver Breeding Laboratories, Wilmington, MA, were randomly assigned to each test group. Animals were isolated for approximately two weeks prior to testing. At the start of the study, rats were approximately 7 (males) and 8 (females) weeks old and weighed approximately 22~7g. (males) and 187±6g. (females). Rats were chosen for this study because they are a common representative species for toxicity studies.

HOUSING: Rats were housed in groups of five segregated by sex. The study was conducted in the vivarium area of Building 320. The study room was maintained at 67-75 °F and 45-57% relative humidity. A photoperiod of 12 hours from 6 a.m. to 6 p.m. was maintained. A two-week gavage study on the same material was housed in the same room as this study. Cages and racks were washed once every two weeks. Absorbent paper was changed under the cages every workday.

FEED AND WATER: Agway Prolab Animal diet (RMH 3200), certified ground chow was fed ad lib. Feed containers were cleaned once during the study. Feed containers were refilled each time feeders were weighed. Water was supplied ad lib. through an automatic watering system. The source of the water was the Monroe County Water Authority. No known contaminants in feed or water were expected which would interfere with the outcome of this study.

IDENTIFICATION: All rats were identified by a unique metal ear tag.

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
TEST SUBSTANCE EXPOSURE: Rats were given 100, 300, or 1000 mg/kg of the undiluted test material by stomach gavage for 21 doses over 29 days. Doses were given 5 days per week except on holidays. Controls received a dose of distilled water equal in volume to that of the highest test group.
Analytical verification of doses or concentrations:
not specified
Frequency of treatment:
once daily for 5 days per week excluding holidays
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
100 mg/kg
Basis:
other: via oral gavage
Remarks:
Doses / Concentrations:
300 mg/kg
Basis:
other: via oral gavage
Remarks:
Doses / Concentrations:
1000 mg/kg
Basis:
other: via oral gavage
No. of animals per sex per dose:
five (5)
Control animals:
other: distilled water via oral gavage
Details on study design:
RANDOMIZATION: All culling and randomization was done by computer-generated lists using the Automated Animal Toxicology System.

BODY AND FEED WEIGHT DETERMINATIONS: Body weights were collected on days 0, 3, 6, 13, 20, 27, and 28. Feed weights were collected on days 3, 6, 10, 13, 16, 20, 24, 27, and 28.
Positive control:
none

Examinations

Observations and examinations performed and frequency:
CLINICAL OBSERVATIONS: Each rat was removed from its cage on the mornings of body weight measurement and examined by a trained technician. Every workday afternoon and on mornings on which body weights were not collected, cageside observations were conducted. Cageside observation included, but was not limited to, examination of the hair, skin, eyes, motor activity, feces, and urine.

HEMATOLOGY AND CLINICAL CHEMISTRY EXAMINATIONS: At the time of necropsy, blood was collected from the posterior vena cava while the rats were under C02 anesthesia. All assays were conducted by the Animal Clinical Analysis Group, HAEL. Hematology tests included: hemoglobin concentration, hematocrit, red blood cell count, white blood cell count, differential white blood cell count, platelet count, red blood cell indices, and examination of the blood smears for cellular morphology. Clinical chemistry tests included: aspartate aminotransferase, alanine aminotransferase, sorbitol dehydrogenase, alkaline phosphatase, creatinine, urea nitrogen, and glucose.
Sacrifice and pathology:
NECROPSY: Rats were fasted overnight, anesthetized with C02, and exsanguinated by severing the posterior vena cava after collecting blood for analysis. Necropsies were conducted according to pathology SOP No. TP 180. The liver and kidneys were weighed. The kidneys were weighed together. Organ/body weight ratios were calculated. The following organs were fixed in 10% buffered formalin: trachea, lungs, heart, tongue, esophagus, stomach, duodenum, jejunum, ileum, cecum, colon, pancreas, liver, salivary glands, kidneys, urinary bladder, pituitary gland, adrenal glands, thyroid glands,
parathyroid glands, thymus, spleen, mesenteric lymph nodes, bone marrow (femoral), brain, testes, epididymides, male accessory sex glands, ovaries, vagina, uterus, Fallopian tubes, and gross lesions. Eyes were fixed in a modified Zenker's (Russell's) fixative. All tissues were examined
microscopically from the control and high dose groups and target organs and gross lesions were examined from other groups.
Statistics:
Mean values were calculated for body weight, feed consumption, organ weights, hematology, and clinical chemistries. All mean data, except feed consumption, were evaluated using the following computer-generated statistical tests: one-way analysis of variance (ANOVA), Bartlett's test, and Duncan's multiple range test using a P value of < 0.05 to indicate statistical significance. Feed consumption was not analyzed statistically because the animals were group housed.

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
Excessive salivation was seen in one female rat immediately after dosing with 1000 mg/kg on Day 27, and in five males immediately after dosing with 1000 mg/kg on Days 27 and 28. No other compound-related clinical abnormalities were observed.
Mortality:
mortality observed, treatment-related
Description (incidence):
Excessive salivation was seen in one female rat immediately after dosing with 1000 mg/kg on Day 27, and in five males immediately after dosing with 1000 mg/kg on Days 27 and 28. No other compound-related clinical abnormalities were observed.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Dosing with the test chemical was well tolerated. Both male and female rats in all dose groups ate and gained weight comparably to the control group. There was no indication of a compound-related effect on either body weight or feed consumption.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
Dosing with the test chemical was well tolerated. Both male and female rats in all dose groups ate and gained weight comparably to the control group. There was no indication of a compound-related effect on either body weight or feed consumption.
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not specified
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
Hematologic data were comparable to controls for all groups receiving the test compound.
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
Serum glucose levels were statistically slightly lower (105 vs 145 mg/dL) in the male 1000 mg/kg group compared to controls. Serum creatinine was statistically slightly higher (0.60 vs 0.69 mg/dL) in the male 1000 mg/kg group compared to controls.
Urinalysis findings:
not specified
Behaviour (functional findings):
not specified
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
Absolute and liver/body weight ratio were increased in males and females given the 1000 and 300 mg/kg doses. Differences in liver/body wt ratios were statistically significant for males and females; absolute liver weights were significant for males only.
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
In addition to high-dose and control tissues, livers, kidneys, stomachs, and gross lesions were processed from the middle and low doses. Compound-related changes were found in the liver (males) stomach (males and females) and probably the kidneys (males).
Details on results:
One female rat (# 438) from the 1000 mg/kg group died on Day 27 following dosing. The cause of death was acute chemical pneumonitis due to
inadvertent intratracheal intubation of the test substance.

Hepatic cells from all 1000 mg/kg males and one 300 mg/kg male were slightly enlarged. Otherwise, hepatocytes appeared within normal limits with no evidence of degenerative changes. Female rat hepatocytes were not affected by compound exposure. Gastric changes were typically those produced by an irritant. In the 1000 mg/kg male group, all rats showed hyperkeratosis and three showed acanthosis of the non-glandular mucosa. At 300 mg/kg (males), two rats showed hyperkeratosis and one showed edema, focal necrosis, and acute inflammatory changes in the non-glandular stomach. Acute inflammatory changes in the glandular stomach of one of these rats were not considered compound-related as similar changes were observed in a control. Stomachs in the 100 mg/kg male rats were comparable to controls. In the female 1000 mg/kg group, four rats had stomachs with hyperkeratosis, one showed acanthosis, and one showed edema of the non-glandular mucosa. At 300 mg/kg, one female rat showed hyperkeratosis and focal necrosis of the non-glandular mucosa. One female rat given 100 mg/kg showed hyperkeratosis of the non-glandular mucosa. Renal changes were seen only in male rats. The effect observed was hyalin droplet formation in proximal renal tubule epithelial cells. It appeared as if exposure to the test compound increased the severity and incidence of hyalin droplet formation in all dose levels and the effect appeared to be dose dependent. Although the data appear to indicate an effect, it is common for normal male rats to have renal hyalin droplets of equal severity and incidence. Therefore, it is possible that the observed effect is actually due to a lower than "normal" incidence in the control. If the effect is actually due to the test compound, the significance of the effect would still be unclear, since the relevance of hyalin droplet formation without other degenerative effects is unknown. It has been recognized that male rats, but not female rats, castrated male rats or other species, have a high normal incidence of hyalin droplet formation and that the severity of this change can be increased particularly by certain branched-chain solvents.

Effect levels

Key result
Dose descriptor:
LOAEL
Effect level:
ca. 100 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
clinical signs
mortality
body weight and weight gain
haematology
clinical biochemistry
organ weights and organ / body weight ratios
gross pathology
histopathology: non-neoplastic

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
Based upon the results of this 28-day repeat dose oral toxicity study, the test article m-diisopropylbenzene (m-DIPB) was well tolerated and toxic findings were limited to mild irritation to the stomach and increased liver weights. A LOAEL of 100 mg/kg also was determined.
Executive summary:

This study investigated the potential toxicity of m-diisopropylbenzene (m-DIPB) following repeated oral doses. The test material was administered by oral gavage to groups of rats at doses of 0, 100, 300, or 1000 mg/kg for 21 doses over 29 days. During this time, body weights, food consumption, and clinical observations were recorded at weekly intervals. At the conclusion of dosing, rats were sacrificed and subjected to routine hematology, clinical chemistry, and histopathological evaluations. m-DIPB was well tolerated when administered by gavage. The exposure resulted in mild irritation to the stomach and increased liver weights. The increase in liver weights was probably an adaptive response since there was no indication of degenerative effects on microscopic examination and no evidence of increased serum enzyme levels. The significance, if any, of the changes in glucose and creatinine levels in the high-dose males is unclear. The changes in glucose and creatinine were within levels commonly encountered in this laboratory and would not be considered clinically significant. The significance of increased renal hyalin droplets in males is also not clear. Based on previous experience, it appears that the effect is probably due to exposure to the test substance but its importance for human health evaluation is not known. Target organs include the stomach due to direct contact, possibly the liver based on increased organ weight, and possibly the kidneys based on the presence of hyalin droplets. The no-effect level was close to but below 100 mg/kg.