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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
short-term repeated dose toxicity: oral
Remarks:
combined repeated dose and reproduction / developmental screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
June 25 - November 19, 2008
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Performed according to OECD test guidelines and GLP principles.
Cross-reference
Reason / purpose:
reference to same study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2009
Report Date:
2009

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): m-xylylene diisocyanate, XDI, CAS no. 3634-83-1
- Physical state: colorless clear liquid

Test animals

Species:
rat
Strain:
other: Crl:CD (SD)
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Hino Breeding Center, Charles River Laboratories Japan, Inc.
- Age at study initiation: 10 weeks
- Weight at study initiation: males 355-394 g and females 240-285 g, females satellite groups 247-279 g
- Fasting period before study: not indicated
- Housing: During acclimatization animals were housed individually in stainless stgeel suspended ages. Animals were paired in males' cages. Dams were housed individually in plastic cages floored with an autoclaved substate of wood chips on Day 18 of pregnancy and thereafter. The dams were housed individually in stainless steel suspended cages on Day 4 of lactation and thereafter.
- Diet: ad libitum to feeders of solid diet (CRF-1, Oriental Yeast Co., Ltd.)
- Water: ad libitum tap water
- Acclimation period: 14 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21.9-24.3
- Humidity (%): 44-63
- Air changes (per hr): 12
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
corn oil
Details on oral exposure:
PREPARATION OF DOSING SOLUTIONS:
The required amount of the test substance was measured out and dissolved in corn oil to a concentration of 40 mg/ml. Dosing preparations containing the test substance at concentrations of 10 and 2.5 mg/ml were prepared by serial dilution of the dosing preparation at 40 mg/ml with corn oil. Preparations were used within 4 hours and 54 minutes of preparation. Dosing volumes 5 ml/kg/day on the most recent body weight.

VEHICLE
- Justification for use and choice of vehicle (if other than water): corn oil
- Concentration in vehicle: same dosing volume.
- Lot/batch no.: V8F7016
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Concentrations of the substance in dosing preparations which were used for both sexes in the test groups on the first day of dosing and for the males in the test groups on the last dosing day were measured by gas chromatography. Concentrations were between 92.9 and 95.1% of target concentration. All results of the examination of specificity, linearity, precision, and intr-assay precision, which were obtained from the present study were within the acceptable criteria. The standard solution was confirmed to be stable in an autosampler for 24 hours. See report study no. 093527, validation of an analytical method for determination of m-xylylene diisocyanate concentration in dosing preparations, June 11, 2008.
Duration of treatment / exposure:
Males treated for 14 days before mating and thereafter 28 days, total of 42 days. Half of the males per group were given a 14-day recovery period.
Females treated for 14 days before mating, during the mating period (max 4 days), and during pregnancy up to Day 6 of lactaction, a total of 44 - 48 days. Females of satellite groups, treated for 42 days, were given a 14-day recovery period.
Frequency of treatment:
daily
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 12.5, 50, 200 mg/kg bw/d
Basis:
actual ingested
No. of animals per sex per dose:
12 males including 6 with a recovery period.
12 females
6 females in satellite group with recovery period.
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: Dose levels based on a preliminary study in which death was noted at 500 mg/kg/day and higher. The dosing length in the present study was to be more than 3 times longer than in the preliminary study, the high dose was selected to be 200 mg/kg/day, at which toxicity was expected to occur and lower dose levels were calculated using a common ration of 4.
- Rationale for animal assignment (if not random): Random sampling method so that the mean body weight and variance were as equal as possible among the groups.
- Post-exposure recovery period in satellite groups: 14 days.
Positive control:
not applicable

Examinations

Observations and examinations performed and frequency:
DETAILED CLINICAL OBSERVATIONS:
- Time schedule: Animals were observed for mortality and clinical signs twice a day, once before and once after administration, once a day during the recovery period and once on the day of necropsy.

BODY WEIGHT: Yes
- Time schedule for examinations: twice a week and on the day of necropsy, with females during pregnancy on Days 0, 7, 14 and 21 and on Days 0, 4 and 6 of lactation.

FOOD CONSUMPTION AND COMPOUND INTAKE:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
Time schedule: approx twice a week

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes
- Time schedule for examinations: approx twice a week

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: After last dosing day and after temination of recovery period.
- Anaesthetic used for blood collection: Yes, by ip injection of sodium pentobarbital
- Parameters examined: according to OECD 422 (1996)

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: see haematology
- Parameters examined: according to OECD 422 (1996)

URINALYSIS: Yes
- Time schedule for collection of urine: Fresh urine and 24-hour urine was collected. For males on day 37 of administration and day 9 of recovery, for females on day 5 of lactation and day 9 of recovery.

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: All animals were observed for FOB before start of administration and once a week during administration.
- Dose groups that were examined: all dose groups
- Battery of functions tested: FOB consisted of observations on: posture, palpebral closure, biting behavior and convulsions; ease of removal from cage, ease of handling, muscle tone, fur conditions, lacrimation, salivation, and respiration. In the open field, frequency of rearing and frequency of grooming for 2 minutes, gait, palpebral closure, consciousness, behavioral abnormalities, and righting reflex.
Sensory reactivity and grip strength in males before necropsy, in 6 females/group on Day 3 of lactation. Spontaneous Motor Activity in males on day 40 of administration and females on day 4 of lactation.

OTHER:
Estrous cycles: Females were observed once a day from the first dosing day to the day before confirmation of copulation.
Mating: After 14 days of treatment, males and females were paired continuously for a maximum period of 14 days until copulation was confirmed.
Nursing conditions: Dams were observed for nursing conditions once a day from days 0 to 4 of lactation.

Pups - F1:
At delivery dams were examined for the number of pups born, their sexes, number of stillbirths, live pups born, and external abnormalities.
Pups were observed for clinical signs and mortality once a day.
Pups were weighed on Day 0 and Day 4 of lactation.
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
Organ weights in males: brain, pituitary, salivary glands, thyroids, thymus, heart, liver, spleen, kidneys, adrenals, testes and epididymides.
Females: number of corpora lutea and number of implantation sites were counted. After necropsy organ weights: same as males + ovaries and uterus.
HISTOPATHOLOGY: Yes
Organs and tissues from males and females of the high dose and control group were examined. When abnormalities were found, e.g. stomach, lower doses were also examined. Organs and tissues examined: heart, lungs, trachea, liver, pancreas, salivary glands, esophagus, stomach, duodenum, jejunum, ileum, cecum, colon, rectum, thymus, spleen, lymph nodes, kidneys, urinary bladder, testes, epididymides, seminal vesicles, prostate, pituitary, adrenals, thyroids, parathyroid glands, brain, spinal cord, sciatic nerves, eyeballs, Harderian glands, bone marrow and bones, testes, ovaries, uterus, vagina, and mammary glands.
Statistics:
Data were tested by Bartlett's test for homogeneity of variance, when variances were homogeneous, Dunnett's test was performed to compare the control group with each of the groups treated with substance. When variance was heterogeneous, Steel's test was performed.
FOB and reproduction/developmental parameters data were tested by Steel's test. Copulation index, fertility index and gestation index were tested by Fisher's exact test.
Effects in stomach: Steel's test was performed. When significant differences were seen, dose-responsiveness was tested by Cochran-Armitage exact test.

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
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
no effects observed
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
no effects observed
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
not examined
Details on results:
CLINICAL SIGNS AND MORTALITY:
No dead or moribund males/females were noted in any group. Salivation was noted in 200 and 50 mg/kg/day group animals after administration. This was considered to be due to the irritancy of the substance and since no further neurological effects were found, not regarded as a systemic effect. During recovery no clinical signs in females and only one male with soiled perineal area was noted. .

BODY WEIGHT AND WEIGHT GAIN:
Body weight was significantly lower in the males at 200 mg/kg/day throughout the administration period and in the females at the same dose level on Day 15 of administration, throughout pregnancy, and on Days 0 and 6 of lactation. Body weight was also lower in the males at 50 mg/kg/day on Days 29 and 36 of administration. However, these findings at 50 mg/kg/day are not considered attributable to the test substance, since (1) the differences from the control group were small, (2) these findings were transient changes, and (3) food consumption was not adversely affected by the test substance at this dose level. During the recovery period, body weight stayed lower in both sexes at 200 mg/kg/day but tended to revert to the normal body weight.

FOOD CONSUMPTION:
In the measurement of food consumption, lower food consumption was noted in the males at 200 mg/kg/day at the beginning of the administration period, but no changes attributable to the test substance were noted in the females at this dose level. During the recovery period, food consumption was higher in the males at 200 mg/kg/day, but this finding is considered to be a recoverable change which occurred after termination of the administration period.

WATER CONSUMPTION:
In the measurement of water consumption, higher water consumption was noted in the males at 200 mg/kg/day at the end of the administration period, in the females at this dose level before the start of mating, and in the females at 200 and 50 mg/kg/day during the lactation period. However, these findings were not regarded as having been caused by the toxicity of the test substance, since all of them were transient changes. During the recovery period, water consumption was higher in the males at 200 mg/kg/day, but no changes attributable to the test substance were noted in the females at this dose level.

HAEMATOLOGY:
No changes attributable to test substance were noted in either sex on termination of the administration period or recovery period.

CLINICAL CHEMISTRY
No changes attributable to test substance were noted in either sex on termination of the administration period or recovery period.

URINALYSIS
No changes attributable to test substance were noted in either sex on termination of the administration period or recovery period.

NEUROBEHAVIOUR:
In the measurement of spontaneous motor activity in the females at 200 mg/kg/day, the ambulatory count and vertical count were lower 70 minutes after administration, and a lower total vertical count and a tendency for total ambulatory count to be lower were noted on termination of the administration period. In the males, no changes attributable to the test substance were noted in the spontaneous motor activity. Regarding FOB, sensory reactivity, and grip strength, no changes attributable to the test substance were noted in either sex at any dose level.

ORGAN WEIGHTS:
In the organ weight measurement on termination of the administration period, a higher relative spleen weight and a tendency for the absolute spleen weight to be higher were noted in the males at 200 mg/kg/day, and higher absolute and relative spleen weights were noted in the females at this dose level. On termination of the recovery period, no changes attributable to the test substance were noted in either sex at any dose level. However, the histopathological examinations on termination of the administration period (see below) shows that there were no changes attributable to the test substance in the spleen in either sex, and hematological examinations shows that the parameters related to the organ weight changes were not affected by the test substance. Therefore, the findings in the spleen weights at 200 mg/kg/day in the present study are considered to be minor changes.

GROSS PATHOLOGY
Test substance-like residuals were noted in the stomach of animals of both sexes at 200 mg/kg bw.

HISTOPATHOLOGY: NON-NEOPLASTIC
In the histopathological examinations, the following findings were noted in the males:
slight or mild hyperplasia of squamous epithelium in the forestomach in all 6 males at 200 mg/kg/day and in 1 male at 50 mg/kg/day, slight or mild hyperkeratosis in the forestomach in all 6 males at 200 mg/kg/day, slight inflammatory cell infiltration in the forestomach in 1 male at 200 mg/kg/day, and cystic changes in the epithelial layer of the forestomach in 1 male at 200 mg/kg/day. In the females at 200 mg/kg/day, the following
findings were noted: slight hyperplasia of squamous epithelium in the forestomach in 3 females, slight inflammatory cell infiltration in the forestomach in 1 female, and cystic changes in the epithelial layer of the forestomach in 1 female. From these findings in the stomach, it can be said that the above-mentioned higher water consumption in both sexes at 200 mg/kg/day was a change to alleviate the irritancy of m-xylylene diisocyanate given to the stomach; the higher water consumption noted in the present study is not judged to be a toxicological change. Since no histopathological changes in the stomach were noted in either sex on termination of the recovery period, higher water consumption occurring during administration will revert to normal water consumption after the discontinuation of administration.

OTHER FINDINGS
In the examinations for reproductive/developmental toxicity in parent animals, no changes attributable to the test substance were noted in the number of estrous cases during the administration period (for 14 days) before the start of mating, copulation index, number of conceiving days, number of pregnant females, fertility index, length of gestation, gestation index, number of corpora lutea, number of implantation sites, implantation index, delivery conditions, or nursing conditions.
In the pups (F1), no changes attributable to the test substance were noted in the number of pups born, number of stillbirths, number of live pups born on Day 0 of lactation, delivery index, birth index, live birth index, sex ratio, number of live pups on Day 4 of lactation, viability index on Day 4 of lactation, clinical signs, body weight on Day 0 or 4 of lactation, appearance, or necropsy findings.

Effect levels

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Dose descriptor:
NOAEL
Remarks:
systemic
Effect level:
50 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Significantly decreased bodyweight in males and pregnant females.
Dose descriptor:
NOAEL
Remarks:
local
Effect level:
12.5 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male
Basis for effect level:
other: Histopathological changes in forestomach and salivation

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
The NOAEL for local effects is 12.5 mg/kg bw/d based on histopathological effects in the forestomach. The NOAEL for systemic effects is 50 mg/kg bw/d based on decreased body weight and salivation.
Executive summary:

Rats were administered 0, 12.5, 50 or 200 mg/kg bw/d of test substance in a study performed according to OECD 422 (1996). Rats were dosed from 14 days before mating during mating and afterwards (total 42 days) for males and during mating period, pregnancy and up to lactation day 6 for females. No mortality occurred. Salivation was noted at 50 and 200 mg/kg bw/d in both sexes. Body weight was decreased in both sexes at 200 mg/kg bw/d. For food and water consumption only transient effects were noted which may be due to irritation of the stomach. No test substance-related effect was seen on haematological, clinical chemistry and urinalysis parameters or at gross pathology. Histopathology revealed an increased incidence of hyperplasia of squamous epithelium and hyperkeratosis in the forestomach in both sexes at 200 mg/kg bw/d. Inflammatory cell infiltration in the forestomach and mild cystic changes in the epithelial cell layer of the forestomach were noted in one male and one female at 200 mg/kg bw/d.

The NOAEL for local effects is 12.5 mg/kg bw/d based on histopathological effects in the forestomach. The NOAEL for systemic effects is 50 mg/kg bw/d based on decreased body weight and salivation.