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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
short-term repeated dose toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1981-04-28 to 1981-05-28 (treatment period)
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:
1982
Report date:
1982

Materials and methods

Test guideline
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)
GLP compliance:
yes
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
Adipic acid, compound with hexane-1,6-diamine (1:1)
EC Number:
222-037-3
EC Name:
Adipic acid, compound with hexane-1,6-diamine (1:1)
Cas Number:
3323-53-3
Molecular formula:
C6H16N2.C6H10O4
IUPAC Name:
hexanedioic acid - hexane-1,6-diamine (1:1)
Details on test material:
- Name of test material (as cited in study report): Nylon Salt 6/6 solution
- Analytical purity: 48-50%
No further data.

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
male and female Charles River Crl: CD (TM)(SD)BR rats
- Source: Charles River Breeding Laboratories
- Age at study initiation: males: 270 - 323 g; females: 179 - 216 g (test day 1)
- Weight at study initiation: ca. 7 weeks (test day 1)
- Housing: individual cages (suspended, open mesh stainless steel)
- Diet (ad libitum): Ralston-Purina Certified Rodent Chow #5002
- Water (ad libitum): tap water from public supply
- Acclimation period: 3 weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°C): ca. 21 - 23 °C (original value: 70 - 74 °F)
No further data

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
water
Details on oral exposure:
PREPARATION OF DOSING SOLUTIONS:
As appropriate to assure accurate dosing, the test material was administered neat and/or diluted with water. Water was be administered to control animals. All doses were administered on a constant volume/kg body weight basis.
Duration of treatment / exposure:
at least 28 days
Frequency of treatment:
daily
Doses / concentrationsopen allclose all
Dose / conc.:
200 mg/kg bw/day (actual dose received)
Dose / conc.:
1 000 mg/kg bw/day (actual dose received)
Dose / conc.:
5 000 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
10 males and 10 females per group
Control animals:
yes, concurrent vehicle

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Each animal was observed twice daily for mortality and as appropriate for clinical signs of toxicity.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Detailed clinical examinations was performed every week.

BODY WEIGHT: Yes
- Time schedule for examinations: Body weight for each animal was determined every week and at sacrifice.

FOOD CONSUMPTION: Yes
Food consumption for each animal was determined every week.

FOOD EFFICIENCY: No

WATER CONSUMPTION: No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at study end
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: No data
- Parameters examined: White blood cell count, red blood cell count, hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at study end
- Animals fasted: No data
- How many animals: all survivors
- Parameters examined: Total protein, blood urea nitrogen, glucose, glutamic pyruvic transaminase, alkaline phosphatase, creatinine, cholesterol, calcium, and thyroxin

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

All animals surviving the study and animals that died or were sacrificed in extremis were submitted for necropsy. Animals surviving to study termination were fasted overnight prior to necropsy. Necropsy procedures included a thorough examination of the nasal, cranial, thoracic, abdominal and scrotal cavities. The following tissues were retained for histopathologic examination (organs in capital letters were weighed): Aorta, adrenals, femur with marrow, brain, esophagus, eyes, TESTES, ovaries, heart, KIDNEYS, LIVER, lung with bronchi, duodenum, jejunum, ileum, colon, urinary bladder, grossly evident lesions, mammary gland, pancreas, pituitary, prostate, salivary gland, sciatic nerve, skeletal muscle, skin, spleen, stomach, thymus, trachea, thyroid, parathyroid, uterus, and mesenteric lymph nodes.
Statistics:
- Dunnett's test (two-tailed) and by inspection for body weight and food consumption data.
- Bartlett's test to assess the variability.
- Hematology and serum chemistry: Dunnett's test and by inspection.
- Terminal body weights and absolute organ weights: analysis of variance and Dunnett's test.
- Organ weights/terminal body weight ratios: Mann-Whitney test using the Bonferoni Inequality Procedure.
- Incidence of microscopic abnormalities: Fisher Exact test with the Bonferoni Inequality Procedure.

Results and discussion

Results of examinations

Clinical signs:
effects observed, non-treatment-related
Description (incidence and severity):
No significant clinical observations were noted at the control, 200 or 1000 mg/kg dose levels. Significant changes at the 5000 mg/kg level included loose stools, rough coats, hypoactivity and red nasal and ocular discharges. Two high dose females also had urine stained fur. One of the females had difficulty in breathing, paleness and was sacrificed in extremis.
Mortality:
mortality observed, treatment-related
Description (incidence):
The highest dose level caused the death or sacrifice in extremis of 10/10 males within 5 days and 6/10 females within 14 days of exposure.
Body weight and weight changes:
effects observed, non-treatment-related
Description (incidence and severity):
The surviving females of the high-dose group had lower mean body weights than the control group at day 8, but their body weights were similar to the controls at study end. 1000 and 200 mg/kg bw produced no body weight changes for either sex.
Food consumption and compound intake (if feeding study):
effects observed, non-treatment-related
Description (incidence and severity):
Initial food consumption data among females at the high dose level reflected a decrease when compared to their controls, but were similar to their controls during the remaining three weeks of testing. No food consumption effect occurred in either sex at 1000 and 200 mg/kg bw.
Haematological findings:
effects observed, non-treatment-related
Description (incidence and severity):
Significant increases in red blood cells and hematocrits in males at the mid and low dose levels were observed (+12% for the mid-dose, +9.6% for the low dose group as compared to the control group). However, the values remained within normal limits of this strain and therefore is not considered as biologically relevant.
Clinical biochemistry findings:
no effects observed
Description (incidence and severity):
Serum chemistry was not altered.
Organ weight findings including organ / body weight ratios:
no effects observed
Description (incidence and severity):
Organ weights among test animals of both sexes that survived to the final necropsy, did not differ significantly from the control group. There was no difference in absolute and relative testes weights between treated groups and controls.
Gross pathological findings:
effects observed, non-treatment-related
Description (incidence and severity):
At necropsy, no changes were observed for the low level males. Animals of the high-dose group had gaseous distention of the stomach (assumed to be due to gasping during the terminal period of life). One mid dose female had renal congestion/redness at the corticomedullary junction. In the high dose group, enlarged adrenals, renal congestion/redness at the corticomedullar were each observed in one female. Two females that died prior to the end of the study had gastric dilatation, and three high dose females which survived to the end of the study had flattening of the gastric mucosal rugae. In the highest dose group 2 males and 3 females had lung congestion, 3 males had cortical congestion/hemorrhages of adrenals.
Histopathological findings: non-neoplastic:
effects observed, non-treatment-related
Description (incidence and severity):
Histopathological changes at levels of 5000 mg/kg bw included renal tubular degenerative changes in 5 of 10 male rats and 3 of 10 female rats. The same dose level produced focal gastric mucosal necrosis in 3 of 10 male rats. Both focal changes were of a non-inflammatory necrotic nature. These changes were not detected in animals receiving 1000 mg/kg bw. Hepatocytic necroses were found in each 2 males and females of the high dose groups and in 1 control female. No changes were found in the pituitaries, testes and ovaries. There were no significant microscopic changes in the mid dose males and females.

Effect levels

Dose descriptor:
NOAEL
Effect level:
1 000 mg/kg bw/day (nominal)
Sex:
male/female
Basis for effect level:
mortality

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
Based on the findings observed, the NOAEL was 1000 mg/kg bw/d under the conditions of this study.
Executive summary:

Abstract

A four week study was conducted using 40 male and 40 female Sprague-Dawley rats administered Nylon Salt 6/6 by gavage (groups of 10 rats/sex). Dosing solutions were prepared daily to give 0, 200, 1000, and 5000 mg/kg/day. Daily checks were made for mortality and obvious signs of toxicity. Weekly body weight and food consumption measurements were taken. All animals were necropsied. Survivors at study termination were bled for hematology and blood chemistry, and their livers, kidneys, arid testes were weighed.

The highest dose level (5000 mg/kg/day) produced the death or sacrifice in extremis of 10/10 males and 6/10 females within 14 days of exposure. Gross pathologic examination of these rats revealed gaseous distention of the stomach. Microscopic findings included renal tubular degenerative changes for both sexes and gastric mucosal changes for males only. At necropsy three of the four surviving females had flat gastric mucosa, but microscopically no significant digestive tract changes were found in these animals. Overall, males were more sensitive to the toxicity of Nylon Salt 6/6.

There was a slight but not statistically significant increase in serum alkaline phosphatase in mid dose level females (1000 mg/kg/day) and statistically significant increases in erythroid parameters in males at the mid and low dose levels (1000 and 200 mg/kg/day respectively). However, the values remained within normal limits making these changes of questionable toxicological significance.

The NOAEL was 1000 mg/kg bw/d under the conditions of this study.