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Repeated dose toxicity: oral

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Administrative data

Endpoint:
sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1992-02-05 - 1992-06-10
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1993
Report Date:
1993

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity in Rodents)
Version / remarks:
1981
Deviations:
no
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid
Details on test material:
Dodecane-12-lactam of Elf Atochem Batch 9611, Purity >= 99.5 % (NMR)

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
- Supplier: Charles River France
- Age at beginning of treatment: about 7 weeks
- Weight at study initiation: 270 g (male) / 200 g (female)
- Environmental conditions:
diet: ad libitum with A04.c complete commercial diet (U.A.R., Villemoisson, France);
water: tap water ad libitum;
room temperature: 22°C (+/- 2°C);
humidity: 40-70 %;
light cycle: 12/24 hours;
air flow: 10-11 changes/hour without recirculation;

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
other: 10% aqueous gum arabic solution supplemented with 0.5 % Tween 80
Details on oral exposure:
- Total volume applied per animal and per gavage: 5 ml/kg bw
- Dose levels: 0 mg/kg BW (control; vehicle alone); 5 mg/kg bw; 25 mg/kg BW; 125 mg/kg bw
- animals were treated once daily
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Identity and concentration of the test substance in the vehicle were verified twice while the study was in progress.
Duration of treatment / exposure:
96 days for reversibility study; 90 days for other animals
Post exposure period: days 97 - 126 (reversibility study)
Frequency of treatment:
- animals were treated once daily for 7 days/week
Doses / concentrationsopen allclose all
Dose / conc.:
0 mg/kg bw/day (actual dose received)
Dose / conc.:
5 mg/kg bw/day (actual dose received)
Dose / conc.:
25 mg/kg bw/day (actual dose received)
Dose / conc.:
125 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
- 20 male and 20 female (for dose groups: 5 mg/ kg bw and 25 mg/kg bw) );
- 25 male and 25 female (for control and dose group 125 mg/kg bw), 5 per sex and group of these in reversibility study
Control animals:
yes, concurrent vehicle
Details on study design:
Post-exposure period: yes (5 male/5 female of the control and dose group 125 mg/kg bw for 30 days after treatment ended)
Positive control:
no

Examinations

Observations and examinations performed and frequency:
- Clinical signs: daily
- Mortality: daily
- Body weight: before treatment starts and then twice weekly
- Food consumption: weekly
- Ophthalmoscopic examination: days 83/84 on all animals (mydriatic eye drops were instilled prior to examination
- Haematology:
days 85 (males)/86 (females): erythrocytes, hemoglobin, packed cell volume, Wintrobe's indices (mean corpuscular volume, hemoglobin, and hemoglobin concentration = MCV, MCH, MCHC), reticulocytes (percentage and abolute; only 10 last animals per sex and group), leukocytes, differential leukocyte count (percentage and absolute), thrombocytes. Coagulation examined on day 97: prothrombin time, activated partial thromboplastin time, fibrinogen level
- Biochemistry:
days 90/91-121: glucose, urea, creatinine, total proteins, albumin, globulins, albumin/globulin ratio, triglycerides, cholesterols, total bilirubin, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatases, gamma-glutamyl transpeptidase, sodium, potassium, chloride, calcium, inorganic phosphate
- Urinalysis:
first 5 animals/sex/group, days 45, 85: volume, pH, proteins, ketone bodies, bilirubins, urobilinogen, specific gravity, glucose, leukocytes, blood, nitrite, erythrocytes, leukocytes, epithelial cells, renal cells, casts, ammonium magnesium phosphate crystals, oxalate crystals, bacteria, parasites
Sacrifice and pathology:
- Macroscopic: skin and subcutaneous tissues, mammary tissue, liver, spleen, kidneys, thymus, heart, lungs, tracheobronchial lymph nodes, urinary bladder, ovaries, uterine tubes, uterine cervix, vagina, testes, epididymides, seminal vesicles, prostate, aorta, sciatic nerve, popliteal lymph nodes, femur and bone marrow, crural muscle, pancreas, esophagus, forestomach, glandular area (stomach), duodenum, jejunum, ileum, cecum, colon, rectum, mesenteric lymph nodes, salivary glands, thyroid glands, parathyroid glands, larynx, tongue, eyes, harderian glands, brain, pituitary, inner ear, femoral bone marrow
- Microscopic: same as macroscopic except for femur and bone marrow, tongue and inner ear
Statistics:
- parametric methods for statistical distributions; Levene test followed by 1-ANOVA and/or Student t test; Bonferroni's method or Scheffe's method for multiple comparisons
- non-parametric methods: Kruskall Wallis test

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Description (incidence and severity):
No clinical abnormality was imputable to treatment.
Mortality:
mortality observed, non-treatment-related
Description (incidence):
45F showed clinical, macroscopic and microscopic signs of esophagus perforation.
54 M showed microscopic signs of aspiration pneumonia.
153M and 170F showed no specific sign accounting for death (stress changes and agonal pulmonary edema). Ground glass appearance of centrilobular hepatocytes, although imputable to treatment, cannot be considered as a cause of death.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
No major difference was observed at any moment of the treatment or reversibility period between groups. The slight decrease in body weight observed in both sexes and in almost every group on days 86 and 91 was probably linked to the examinations performed at the end of treatment
(mainly fasting for blood sampling).
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
no effects observed
Description (incidence and severity):
No difference was observed at any moment of the treatment or reversibility periods between
groups.
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
no effects observed
Description (incidence and severity):
No abnormality imputable to treatment was observed
Haematological findings:
no effects observed
Description (incidence and severity):
No difference imputable to treatment was observed between groups.
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
The variations imputable to treatment were observed on D90 {end of treatment period) at the high dose level (125 mg/kg/d):
a slight increase in albumin and total protein levels in females only {39.3 g/l vs 37.3 g/l for albumin and 78.4 g/l vs 75.1 g/l for total proteins),
a moderate increase in potassium levels in males only ( 5.25 mM vs 4.74 mM).
On D121 (end of reversibility period), no statistically significant difference remained.
The following variations were not imputed to treatment:
the statistically significant increase in glucose levels observed on D90 in high-dose males was
too slight to be biologically significant (6.00 mM vs 5.55 mM), the increase in triglyceride levels observed on 0121 in the females of the control group (1.18 mM on 0121 vs 0.59 mM on 090) was linked to an isolated marked increase observed in one female (no. 28, 3.21 mM), the statistically significant decrease in total bilirubin levels observed on D90 in high-dose males and females was too slight to be biologically significant ( 1.5 µIM vs 1.9 µM in males, 2.0 µM vs 2.3 µM in females), the statistically significant decrease in ASA T levels observed on D90 in high-dose males has no biological significance (56 IU/l vs 66 IU/l),
the numerous statistically significant differences observed for sodium (D90 in high-dose males and females, D121 in males) and chlorides (D90 in treated males, D121 in males) were slight and not biologically significant.
Urinalysis findings:
effects observed, treatment-related
Description (incidence and severity):
The modifications attributed to treatment were the following:
moderate increase in potassium excretion in mid- and high-dose males (25 and 125 mg/kg/d) on D 45 (2728 and 2416 mc.moles vs 1774 me. moles),
moderate increase in sodium concentration and excretion in high-dose males (125 mg/kg/d) on D45 (40 mM vs 23mM and 802 mc.moles vs 370 mc.moles).
These changes were no longer observed on D85.
The following changes were not attributed to treatment because they were slight or not related to the dose:
slightly increased pH in low-dose females on D45, (7.7 vs 7.0) and decreased pH in mid-dose females on D85, (6.2 vs 7.7), increased specific gravity in low- and mid-dose females on D85 (1.025 and 1.027 vs 1.017).
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
effects observed, non-treatment-related
Description (incidence and severity):
No variation imputable to treatment was observed.
The following statistically significant variations were not attributed to treatment because they were slight and not biologically significant:
slight decrease in thymus absolute weight in mid-dose males on D97 (372 mg vs 445 mg),
slight increase in liver relative weight in low-dose females on D97 (33.653g/kg vs 31.169 g/kg),
slight increase in heart relative weight in high-dose females on D97 (3. 77 g/kg vs 3.58 g/kg),
slight decrease in pituitary relative weight in high-dose females on D97 (49.3 mg/kg vs 53.5 mg/kg).
Gross pathological findings:
effects observed, non-treatment-related
Description (incidence and severity):
The study of the macroscopic lesions observed and of their incidence did not reveal any lesion
imputable to treatment.
The main lesions observed in the animals found dead are the following:
45F Control group, found dead on D83.
Perforation of esophagus, mass under foreleg and large quantity of blood in the stomach.
54M Low-dose group (5 mg/kg/d), found dead on D35.
Marked general congestion of the lungs, congestion or dark discoloration of various
organs (adrenals, thymus, popliteal lymph nodes, brain).
153M High-dose group (125 mg/kg/d, found dead on D56.
Early autolysis, congestion of the lungs and presence of foam in the bronchi, congestion
of thymus, liver pale discoloration, meteorism.
170F High-dose group (125 mg/kg/d), found dead on D63.
Congestion of the lungs and presence of foam in the bronchi, congestion or dark
discoloration of various organs (adrenals, ovaries).
The cause of these deaths is discussed in section mortality.
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
effects observed, non-treatment-related
Description (incidence and severity):
Liver: The administration of LAUROLACTAM resulted in a modification of the appearance of the cytoplasm of centrilobular hepatocytes (ground glass appearance) in a few males from group 2
(25 mg/kg/d) and 3 (125 mg/kg/d).
Thyroid: an increase in the incidence of the columnar appearance (and vacuolar in a few cases) of the follicular epithelium was observed in animals from groups 2 and 3. It was not considered
positively attributable to the test compound, the variation being minor.

Animals nos.45F (Group 0- control), 54M (Group l - 5 mg/kg/d), 153M and l70F (Group 3- 125 mg/kg/d) dead during the study on days 83, 35, 56 and 63, respectively.
In addition to congestive changes of little significance, these animals presented:
animal no. 45F,
stress changes (chronic lymphoid atrophy of the spleen and thymus),
• changes giving evidence of gavage-induced trauma (purulent, granulomatous or fibrous
inflammatory cell infiltration of the esophagus, salivary glands and retromandibular
lymph nodes with presence of vegetal particles);
Death is probably secondary to these changes.

- animal no. 54M, edematous subacute aspiration pneumonia (with presence of vegetal
particles) and subacute or granulomatous inflammatory cell infiltration of the larynx and
trachea with hemorrhage of the larynx and tracheobronchial lymph nodes;
Death is probably secondary to pneumonia.

- animal no. 153M,
• ground glass appearance of centrilobular hepatocytes (see above),
• stress changes (adreno-cortical hyperplasia),
• slight changes of alveolar and perivascular pulmonary edema, probably agonal;
The cause of death could not be determined.

animal no. 170F,
• stress changes (lymphoid atrophy of the spleen),
• alveolar and perivascular pulmonary edema, probably agonal;
The cause of death could not be determined.


Other findings:

They are physiological or belong to the spontaneous pathology of the species and are reported in the summary tables, thyroid adenoma of animal no. 152M (Group 3 - 125 mg/kgfd) and leukemia of animal no. 110M (25 mg/kg/d) included.

Electron microscopy

The liver was not examined because no sample was taken from the animals presenting the hereabove-mentioned hepatic changes, for electron microscopic examination.
The examination of the kidney was not considered necessary.

In conclusion, the administration of LAUROLACTAM resulted in a ground glass appearance of centrilobular hepatocytes in a few males from the dose of 25 mg/kg/d upwards.

One Group 0 animal was found dead following a gavage-induced trauma; one Group I animal (5 mg/kg/d) died of aspiration pneumonia; two Group 3 animals (125 mg/kg/d) died presenting a few
stress changes and changes of pulmonary edema probably agonal, which could not account for death.



Histopathological findings: neoplastic:
no effects observed
Details on results:
TOXIC RESPONSE/EFFECTS BY DOSE LEVEL:
- Mortality and time to death:
0 mg/kg: 1 female, day 83, esophagal perforation
5 mg/kg: 1 male, day 35, aspiration pneumonia
25 mg/kg: no mortalities
125 mg/kg 1 male, 1 female, days 56, 63, cause for mortality not obvious: Animals showed no specific signs accounting for death (stress changes and agonal pulmonary edema). Ground glass appearance of centrilobular hepatocytes (the male), although imputable to treatment, could not be considered as a cause.
- Clinical signs: no treatment releated abnormality detected
- Body weight gain: no treatment releated abnormality detected; slight decrease in both sexes in almost every group on days 86 and 91 was probably linked to the examinatins performed (mainly fasting for blood sampling)
- Food consumption: no treatment releated abnormality detected
- Ophthalmoscopic examination: no treatmend releated abnormality detected
- Clinical chemistry: high dose group: moderate increase in potassium (males), no longer statistically significant by end of reversibility period (day 121); slight increase (females only) in total proteins (78.4 vs 75.1 g/l) and albumin (39.3 vs 37.3 g/l)
- Haematology: no treatment releated abnormality detected; Coagulation: no major differences with no biological significance
- Urinalysis:
day 45: moderate increase in potassium excretion of medium / high dose males (2728 / 2426 vs 1774 mc.moles);
moderate increase in sodium concentration and excretion of high dose males (40 vs 23 mM; 802 vs 370 mc.moles);
day 85: no treatment releated abnormality detected
- Organ weights: no treatment related abnormality detected
- Gross pathology: no treatment related abnormality detected
- Histopathology: ground glass appearance of centrilobular hepatocytes in 4 males each of mid and high dose groups

Target organ: liver
All observed effects returned to normal values after a recovery period of 30 days.

Effect levels

open allclose all
Key result
Dose descriptor:
NOAEL
Effect level:
25 mg/kg bw/day (nominal)
Sex:
male/female
Basis for effect level:
clinical signs
Dose descriptor:
LOAEL
Effect level:
125 other: mg/kg
Sex:
male/female
Basis for effect level:
clinical biochemistry

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

no further relevant remarks

Applicant's summary and conclusion

Conclusions:
The aim of this three month oral toxicity study was to assess the subchronic toxicity of the test item LAUROLACTAM to the rat at the dose levels of 0, 5, 25 and 125 mg/kg/d. In conclusion, no toxic effect was observed at 5 and 25 mg/kg/d whereas signs of slight toxicity were observed at 125 mg/kg/d after oral administration of the test item in rats. Taking all findings into account, 25 mg/kg/d constitutes a No-Observed-Adverse-Effect-Level (NOAEL) for oral administration of the test item in male and female rats under conditions of this study..
Executive summary:

The aim of this three month oral toxicity study was to assess the subchronic toxicity of the test item LAUROLACTAM to the rat at the dose levels of 0, 5, 25 and 125 mg/kg/d.

At the dose level of 5 mg/kg/d, no modification of the parameters studied was observed.

From the dose level of 25 mg/kg/d, a moderate and transient increase in potassium excretion and ground glass appearance of centrilobular hepatocytes were observed in a few males.

At the dose level of 125 mg/kg/d, blood examinations revealed a slight increase in albumin levels in females and a moderate increase in potassium levels in males. Sodium excretion was also increased in males. Two animals were found dead at this dose without clinical sign or microscopic lesion which could explain death.

Consequently, 5 and 25 mg/kg/d can be considered as non toxic doses as there was no modification at 5 mg/kg/d and no clinical or biochemical modification related to the slight hepatic changes observed in a few males at 25 mg/kg/d.

At the dose level of 125 mg/kg/d, the slight biochemical modifications observed in femals and the histological lesions noted in a few males can be considered as the first signs of a moderate toxic effect on the liver. However, the mortality observed at this dose cannot be directly attributed to a toxic effect of the compound as no significant clinical signs or pathological changes were found.

In conclusion, no toxic effect was observed at 5 and 25 mg/kg/d whereas signs of slight toxicity were observed at 125 mg/kg/d after oral administration of the test item in rats. Taking all findings into account, 25 mg/kg/d constitutes a No-Observed-Adverse-Effect Level (NOAEL) for oral administration of the test item in male and female rats under conditions of this study..