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Administrative data

acute toxicity: other routes
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non GLP study with no guideline available however, a well documented scientific paper.

Data source

Reference Type:
Nitric Acid-Induced Injury in the Hamster Lung
Coalson JJ and Collins JF
Bibliographic source:

Materials and methods

Test guideline
no guideline available
GLP compliance:
Limit test:

Test material

Constituent 1
Chemical structure
Reference substance name:
Nitric acid
EC Number:
EC Name:
Nitric acid
Cas Number:
Molecular formula:
nitric acid
Test material form:
other: liquid
Details on test material:
- Name of test material (as cited in study report): Nitric acid

Test animals

hamster, Syrian
Details on test animals or test system and environmental conditions:
- Source: Charles River Breeding Laboratories, Wilmington, Massachusetts
- Weight at study initiation: at least 120 g
- Diet: routine diet Wayne rodent chow was provided ad libitum
- Water: ad libitum

Administration / exposure

Route of administration:
other: transorally into the trachea
other: saline
Details on exposure:
Treated animals received 0.5% nitric acid, pH 1.6, in 0.5 mL saline/100 g body weight, administered transorally into the trachea. Control animals for all study groups received 0.5 ml saline/100 g body weight. The hamsters from the experimental and control groups were killed with Euthanasia solution at 3, 7, 14, 28, 32, 35, 45, and 60 days.
Control animals:
Details on study design:
- Necropsy of survivors performed: yes
- Other examinations performed: organ weights, histopathology, morphometric studies, and biochemical analysis.
Differences among the test substance groups and the control group were tested for significance using Duncan's multiple range test and Dunnett's multiple comparisons procedure.

Results and discussion

Effect levels
Dose descriptor:
other: No NOAEL identified
Effect level:
other: specific mortality data not presented
Remarks on result:
other: Several animals died before day 3 and showed severe haemorrhagic pulmonary oedema.
Several animals died before day 3 and showed severe haemorrhagic pulmonary oedema. (Exact number of animal deaths not provided.)
Clinical signs:
At day 3, mixed alveolar haemorrhage and oedema were present.
Body weight:
Biochemical results showed that hamsters given nitric acid showed a much larger loss in total body weight than the control animals at 3 days. The body weights of animals killed at 35 days was similar in the control and nitric acid study groups and was comparable to control animals killed at 3 days.
Gross pathology:
There was a significant increase in lung wet and dry weights relative to the controls at 3 days. During the course of the experiment, both wet and dry lung weights returned toward normal values, but throughout the experiment, lung wet and dry weights in the nitric acid-treated animals were significantly greater than control values. Total collagen was unchanged at 3 days but was significantly greater than control values after 14 days. Elastin was also significantly increased after 14 day.
Other findings:
Selected electron microscopic studies, performed on nitric acid bronchiolar lesions at 7, 14, and 21 days, demonstrated that the Clara cell was the predominant reparative bronchiolar epithelial cell. Although the bronchiolar epithelium contained a few ciliated cells, most were non-ciliated Clara cells whose cytoplasm contained a few free ribosomes, abundant mitochondria, smooth endoplasmic reticulum and few if any secretory granules. Occasional alveolar epithelial type II cells were seen among the bronchiolar cells. Rarely, bronchiolar cells contained lamellar-like inclusions, but these were not membrane-bound.

There was no significant difference in the mean linear intercept determinations between the nitric acid-treated and control animals. The internal surface area determinations within the nitric acid treated groups were not significantly different from one another. However, there were significant differences in lung volume and internal surface area determinations when the treated groups were compared to the control group at each time period (P<= 0.001). Lung volumes of control animals were approximately double those of the nitric acid-treated animals. There were no significant differences between the body weights of the control and nitric acid-treated groups; they ranged from 130 to 169 g at necropsy. The loss of volume in the treated animals probably resulted from the peribronchial/bronchiolar fibrosis.

When the point-count data were analyzed, the percentage involvement of airway dilatation and/or surrounding alveolar wall fibrosis, expressed as a percentage involvement of the parenchyma of the lung, was 0% in the control group of animals, and in the treated animals: 40% at day 35, 33% at day 45 and 19% at 60 days, indicating a gradual improvement in the evolution of the disease process

Any other information on results incl. tables

Striking bronchial/bronchiolar epithelial loss was evident, and residual epithelial cells showed apical cytoplasmic blebs. The airway lumina contained a coagulum of rich oedema fluid, a few extravasated RBCs, and necrotic epithelial cells. Frequently, the bronchiolar epithelium had sloughed and thick hyaline membranes containing fibrin covered the denuded epithelial surface or formed rounded aggregates within the bronchiolar lumina. One of the six animals showed an exudate of polymorphonuclear leucocytes within the bronchioles and surrounding alveoli, suggesting early bronchopneumonia, probably secondary to aspiration of orophargyneal flora following the transoral instillation.

At 7 days, reparative processes were evident. Extensive bronchiolization of alveolar walls immediately adjacent to the damaged bronchioles was a prominent feature. Most of the distal airspaces involved at 3 days with pulmonary oedema were fluid-free at this time period. Many lipid-laden macrophages were in alveoli, secondary to the obstructive airway lesions. In addition to the marked epithelial hyperplasia, the trichrome stain revealed an increase in collagen deposition. Elastic fibres showed early fibre fragmentation in the alveolar walls surrounding the airways.

At day 14, light microscopic findings showed well-expanded central and peripheral airways, multiple sites of extensive bronchiolization, a few residual sites of oedema or haemorrhage, foci of foamy macrophages within the alveolar spaces, and pigment in the affected airway walls. Three of the 11 animals showed a coexistent organizing pneumonitic process. In all the test substance treated hamsters, trichrome stains revealed definite collagen depositiion in the bronchial and bronchiolar walls with extension into the surrounding alveolar walls. Aldehyde fuchsin-stained preparations showed fragmented elastin fibres in these same sites. The areas of bronchiolar epithelialization contained ciliated and non-ciliated cells.

At day 21 days, striking hyperplasia of the bronchiolar epithelium was still evident. The epithelial proliferation often appeared glandular and was surrounded by connective tissue proliferation. The trichrome and aldehyde fuchsin stains showed striking collagen depositions and elastic fibre fragmentation respectively. Occasional bronchioles showed polypoid masses of granulation tissue within the bronchiolar lumina, i.e. obliterative bronchiolitis, but this was not a widespread finding.

At 28 days, small bronchi and bronchioles were ectatic and showed peribronchiolar and surrounding alveolar wall fibrosis. A few residual airways showing hyperplastic bronchiolar epithelium were still evident, but were not as numerous as in the 14 and 21 day specimens.

At 35 days, the mixed airway lesions patter persisted but at 45 and 60 days, the airway dilatation lesion was dominant. Adjoining alveolar walls showed mild interstitial thickening.

Applicant's summary and conclusion

Intratracheally instilled nitric acid yields a spectrum of airway changes including acute bronchitis, bronchiolitis, obliterative bronchiolitis, bronchiectasis and bronchiolectasis in the hamster. Some deaths among the treated animals occurred prior to 3 days. The model identified prolonged insult to the airways which develops rapidly and persists over a long period of time.