Dibutylamine

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study, but limited to the respiratory system and reproductive organs

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

2003

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)

Deviations:

yes

Remarks:

limited to the respiratory system and reproductive organs

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Dibutylamine

EC Number:

203-921-8

EC Name:

Dibutylamine

Cas Number:

111-92-2

Molecular formula:

C8H19N

IUPAC Name:

N-butylbutan-1-amine

Details on test material:

Di-n-butylamine

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, Germany
- Age at study initiation: approx. 8 weeks
- Weight at study initiation: males: 279 - 290 g; females: 181 - 186 g
- Housing: individually
- Diet: Pellets 1324 N (Altromin International, Lage, Germany) ad libitum
- Water: filtered tap water ad libitum
- Acclimation period: 3 w (including training with the inhalation tube)

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 - 24 C°
- Humidity (%): 30 - 70%
- Air changes (per hr): 15 - 20x
- Photoperiod: 12hrs dark / 12 hrs light

Administration / exposure

Route of administration:

inhalation

Type of inhalation exposure:

nose only

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

direct flow nose-only inhalation system, individually exposure

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

GC-FID; measured concentrations: 50.6 +-5.5, 142 +-9.7, and 448.2 +-16.0 mg/m3 (gas-phase, analytical)

Duration of treatment / exposure:

91 d with interim sacrifices after 3 and 28 d

Frequency of treatment:

6 h/d; 5x/week

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

50 mg/m³ air (nominal)

Doses / concentrations 2

Dose / conc.:

150 mg/m³ air (nominal)

Doses / concentrations 3

Dose / conc.:

450 mg/m³ air (nominal)

No. of animals per sex per dose:

5/sex/treatment for the 3 and 28 days exposure groups and 10/sex/treatment for the 91 days exposure groups.

Control animals:

yes, concurrent no treatment

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations: weekly

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: No

CLINICAL CHEMISTRY: No

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes, all animals were subjected to a macroscopic examination.
HISTOPATHOLOGY: Yes, samples of all organs and tissues were taken and fixed for possible histopathological examination. Histopathological examinations were carried out on the organs of the repiratory tractus, i.e. nasopharyngeal tissues, trachea, lungs (left lobe) and lung associated lymph
nodes of all animals subjected to broncheo-alveolar lavage.
In a follow-up study conducted in 2010, the reproductive organs (testes, epididymides, seminal vesicles, prostate and coagulating glands in males; vagina, uterus with cervix and ovaries with oviducts in females) were examined.

Other examinations:

Organ weights: from all animals the lung weights (including trachea) were determined. No other organ weights were measured.

Broncho-alveolar lavage (BAL): On 5 rats per dose group at necropsy on days 3, 28 and 91. The right lung lobes (1-4) were rinsed two times with 3.5
ml (males) or 2.7 ml (females) saline. Subsequently, a differential leucocyte count (macrophages, granulocytes and lymphocytes) count was performed and a number of relevant biochemical indicators of lung damage (Lactate dehydrogenase, beta-glucuronidase and total protein) were determined.

Statistics:

P<0.05 considered statistically significant.
ANOVA (analysis of variance) for weights, food, and BAL.
Two-tailed Dunnett´s test: means of groups vs. corresponding control group.
Fisher´s exact test: for frequency data.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

slight convulsions in some animals of the high dose group during the first 3 days directly after exposure

Mortality:

mortality observed, treatment-related

Description (incidence):

slight convulsions in some animals of the high dose group during the first 3 days directly after exposure

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

significantly reduced (p<0.05) terminal body weight in males at 150 and 450 mg/m³. Reduced body weights also in low dose males and all female groups (dose related), but without gaining level of statistical significance.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

reduced

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not specified

Organ weight findings including organ / body weight ratios:

not examined

Description (incidence and severity):

only lung examined

Gross pathological findings:

no effects observed

Neuropathological findings:

not specified

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Only local irritation and sequelae in nasal cavities, i.e only in the upper respiratory tract, in all exposed groups; o sex differences. No changes in male and female reproduction organs at any dose level.

Histopathological findings: neoplastic:

no effects observed

Other effects:

not specified

Details on results:

CLINICAL SIGNS AND MORTALITY
There were no clinical signs of intoxication of the animals, except slight convulsions observed in some animals of the highest concentration group (450 mg/m3) directly after exposure in the first days of exposure. These may at least partly be due to defensive reaction of the animals to the exposure.

BODY WEIGHT AND WEIGHT GAIN
at 50, 150 and 450 mg/m3, a dose related decrease in body weight gain was noted in males and females of the mid and high dose groups when exposed during 28 days and in males and females of all dose groups when exposed during 91 days. The effects were more prominent in males than in females. The terminal body weight on day 91 was statistically significantly reduced (p<0.05) only in males at 150 and 450 mg/m³, whereas the female terminal body weight was slightly reduced and did not gain statistical significance.

FOOD CONSUMPTIONA
At 50, 150 and 450 mg/m3, a dose related decrease was noted in males and females of the mid and high dose groups when exposed during 28 days and in males and females of all dose groups when exposed during 91 days. The effects were more prominent in males than in females.

ORGAN WEIGHTS: LUNG WEIGHT: only significantly increased in females of the high-dose group.

GROSS PATHOLOGY
No treatment-related gross pathology findings were observed.

HISTOPATHOLOGY: NON-NEOPLASTIC
Histopathological changes were noted in the nasal cavities. After 3 and 28 days of exposure these changes were found in the high dose only and consisted on day 3 of erosive-ulcerative areas. On day 28, histopathological findings in the nasal cavity as noted on day 3 were not found. The changes observed in the nasal cavity were characterized by inflammation cells in the mucosa, squamous cell metaplasia and adaptive hyperplasia of Goblet cells . Findings noted in high dose animals on day 28 persisted on day 91 of exposure . In addition, adaptive changes, including hyperplasia of Goblett cells, were also noted in the low and intermediate dose groups. In closure, hyperplasia of the Broncheo Associated Lymphoid Tissue (BALT) and lymphoid hyperplasia in the Lung Associated Lymph Nodes (LALN) was noted incidentally in treated animals after 3 days exposure (intermediate and high dose groups), after 28 days exposure (low and intermediate dose groups) or after 91 days exposure (low, intermediate and high dose groups), however no treatment-related distribution or sigificant increase of the incidences were noted.

OTHER:
Broncheo-alveolar lavage: differential leucocyte counts remained within the range as controls. There were no biologically significant changes observed in selected biochemical parameters for the determination of lung damage.

For the reproductive organs:
GROSS PATHOLOGY:
3-Day Exposure Group: no macroscopic findings were observed in the reproductive organs
28-Day Exposure Group: A single female of the 150 mg/m3 DBA dose group showed a macroscopic dilatation of both uterine horns, which histologically corresponded to estrus cycle-dependent luminal dilatation (by fluid).
91-Day Exposure Group: A single male of the 450 mg/m3 DBA exposure group showed a slight enlargement of the prostate which, however, could not be correlated to a microscopic change. Dilatation of both uterine horns was observed in 1/5, 4/10, 2/10 and 1/10 females of the clean air control, 50, 150 and 450 mg/m3 DBA dose groups, respectively, which histologically corresponded to estrus cycle-dependent luminal dilatation (by fluid).

HISTOPATHOLOGY:
3-Day Exposure Group:Test compound-related microscopic changes were not observed in the reproductive organs of either males or females. Incidental changes occurred in the prostate, uterus and vagina, while all other reproductive organs were within normal limits.
28-day Exposure Group:Test compound-related microscopic changes were not observed in the reproductive organs of either males or females. Incidental changes occurred in the testes, epididymides, prostate and uterus, while all other reproductive organs were within normal limits.
91-Day Exposure Group: Test compound-related microscopic changes were not observed in the reproductive organs of either males or females. Incidental changes occurred in the testes, epididymides, prostate, uterus and vagina while all other reproductive organs were within normal limits.

Effect levels

1

Dose descriptor:

NOAEC

Remarks:

local effects

Effect level:

50 mg/m³ air

Sex:

male/female

Basis for effect level:

other: local irritation and sequelae in nasal cavities, i.e only in the upper respiratory tract

2

Dose descriptor:

NOAEC

Remarks:

systemic toxicity

Effect level:

450 mg/m³ air

Sex:

male/female

Basis for effect level:

other: see Remarks

Remarks on result:

other:

Remarks:

no systemic effects observed

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

Local irritation and sequelae of the upper respiration tract, i.e. the nasal cavaties, were the prominent effects in a 90-day rat inhalation study with the test substance at 50, 150, and 450 mg/m³. Lower respiratory tract irritation was marginal. Male and female reproductive organs were not affected at any dose level. NOAEC for local irritation is considered to be 50 mg/m³. Local irritation may be associated with the observed decrease of food intake in both genders, and, hence, also with a dose-dependent decrease of male and female body weight gain over the entire study period. No systemic effects were observed. Therefore, the systemic NOAEC is considered to be 450 mg/m³, which is the highest dose tested.

Executive summary:

The effect of the test substance (0, 50, 150, and 450 mg/m³) on the respiratory tract was examined in an OECD guideline 413 inhalation study (90-days) using rats and conducted under GLP conditions. Interim sacrifice was made after 3 and 28 days of exposure. Five male and female Wistar rats were used in the control groups and in the treatment groups with sacrifice at days 3 and 28; ten rats per sex were used in the 91-day treatment groups. The study focused on effects on the upper and lower respiration tract, and the full list of parameters that is included in the OECD 413 guideline was not in the scope of this study. In a follow-up study, the male and female reproductive organs were subjected to histopathological examinations.

 

The results indicate a pronounced irritation of the nasal cavities, i.e. the upper respiratory tract, on day 3 of exposure in the groups at 450 mg/m³, substantiate by ulceration, epithelial erosions, squamous metaplasia of the respiratory epithelium, mucosal inflammatory cell infiltration, submucosal hemorrhage and mucous cell hyperplasia in most animals. Due to adaption the lesions were less pronounced in groups at 28 and 91 days of high dose exposure. Mucous cell hyperplasia was also seen in the low and intermediate dose groups on days 28 and 91, along with mucosal and/or submucosal edema in 10% of the animals at 50 mg/m³ on day 91. The statistical significance of these findings was not reported. However, the findings are understood to indicate an adaptive response to local irritation. Effects in the lower respiration tract and in the lung were surprisingly marginal at all dose levels (Fraunhofer ITEM, 1999; 2003). Therefore, the NOAEC for local irritation is considered to be 50 mg/m³ in this subchronic rat inhalation study.

 

Local irritation may be associated with the observed decrease of food intake in both genders, and, hence, also with a dose-dependent decrease of male and female body weight gain over the entire study period. This was more pronounced in males than in females. The decrease of the terminal body weight gained significance (p<0.05) in males at 150 and 450 mg/m³, but not in females (Fraunhofer ITEM, 1999; 2003). No systemic effects were observed. Therefore, the systemic NOAEC is considered to be 450 mg/m³, which is the highest dose tested.

 

No histopathological changes were noted in male and female reproductive organs (testes, epididymides, seminal vesicles, prostate and coagulating glands in males; vagina, uterus with cervix and ovaries with oviducts in females) at any dose level that were attributable to the test substance. Only incidental changes were observed without any dose relationship. Therefore, the NOAEC for the male and female reproductive organs was 450 mg/m³ in this 90-day rat inhalation study (Fraunhofer ITEM, 2010).

 

The study is reliable and well documented within its scope (focus on respiratory tract and reproductive organs) and suitable for assessment.