Hexamethylene diisocyanate

Respiratory sensitisation

Administrative data

Endpoint:

respiratory sensitisation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1996

Report date:

1996

Materials and methods

Test guideline

Qualifier:

no guideline available

Principles of method if other than guideline:

The technical exposure criteria specified in OECD Guideline No. 403 and the corresponding EC Guideline 892/69/EEC (1992) were fulfilled insofar as these are applicable to this study. General recommendations on the techniques used for the generation and characterization of atmospheres (ASTM E 981-84; Alarie, 1973) were observed. Specific, internationally harmonized test procedures for experiments to assess the lung sensitization potential of low- or high-molecular weight compounds are not currently available.

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Hexamethylene diisocyanate

EC Number:

212-485-8

EC Name:

Hexamethylene diisocyanate

Cas Number:

822-06-0

Molecular formula:

C8H12N2O2

IUPAC Name:

1,6-diisocyanatohexane

Test animals

Species:

guinea pig

Strain:

other: Dunkin-Hartley Pirbright-White

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River (Sulzfeld, Germany)
- Age at study initiation: approx. 2 weeks
- Housing: 4 per cage
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 2
- Humidity (%): approx. 50
- Air changes (per hr): approx. 10
- Photoperiod (hrs dark / hrs light): 12 / 12

Test system

Route of induction exposure:

other: intradermal and inhalation

Route of challenge exposure:

inhalation

Vehicle:

other: intradermal: desiccated corn oil - inhalation: vapour

Concentration:

see details on study design

No. of animals per dose:

8

Details on study design:

Groups of eight female guinea-pigs were intradermally induced once per day on days 0, 2, and 4 (injection volume: 100 µl / 0.3 % solution in desiccated corn oil and one additional group of animals were exposed for five consecutive days (days 0 - 4) by inhalation (duration of exposure: 3 hrs/day) to average concentrations of 1,6 -hexamethylene diisocyanate (vapour) of 27.4 mg/m3 air. The latter group of animals received an additional single intradermal induction on day 0. Control animals received the vehicle alone (intradermally) under othenvise identical conditions (no inhalation exposure). During the recovery period (starting on day 21) a hapten-challenge (target concentrations: approximately 0.5 mg hapten/m3 air) was performed (challenge duration: 30 min). One day before and one day after the hapten-challenge an acetylcholine bronchoprovocation challenge (stepped concentrations in steps of 0.1%, 0.2%, 0.4% and 0.8%, w/v; duration of each 15-min) was performed. Following day 28 all guinea pigs were challenged again with the respective guinea pig serum albumin (GPSA) conjugate of the hapten (mean concentration: approximately 50 mg/m3 air). During and after challenge exposures immediate-onset respiratory reactions were evaluated by measurement of respiratory rate, tidal volume, respiratory minute volume, inspiratory and expiratory times, and peak expiratory flow rate. Additional parameters were derived mathematically. In some of the groups also measurements for delayed-onset responses were incorporated. On day after the GPSA-conjugate challenge, animals were sacrificed, and the lungs, including trachea and lung associated lymph nodes, were examined histopathologically. The weight of the excised lungs was determined. At sacrifice blood was sampled for serological examinations.

Results and discussion

Results:

Following induction, inflammatory skin reactions were observed. Also during the inhalation induction, signs indicative of respiratory tract irritation occurred. During or following hapten-challenges, the incidence of immediate-onset type respiratory reactions were roughly the same in all groups whereas during or following conjugate-challenges immediate-onset respiratory reactions occurred in a higher incidence in the 1,6-hexamethylene diisocyanate (HDI) sensitized groups when compared to the control groups. The comparison of both routes of induction demonstrates that the incidence of responding animals was not appreciably different when additional inhalation induction exposures were made. The acetylcholine bronchoprovocation challenge demonstrated that previous inhalation induction exposures to HDI do not evoke a conspicuous non-specific bronchial hyperreactivity. The histopathological investigations revealed inflammatory responses in those groups receiving inhalation induction exposures (bronchiolitis). Independent on the route of induction evidence of a specific airway eosinophilia and eosinophil infiltration into lung associated lymph nodes, a hallmark of allergic airway hyperresponsiveness, was observed. The serological investigations revealed a marked increase in anti-HDI IgG1-antibody titres.

Applicant's summary and conclusion

Interpretation of results:

sensitising

Executive summary:

When animals that were sensitized intradermally or by inhalation and were subsequently challenged by inhalation with the respective hapten of 1,6 -hexamethylene diisocyanate no conclusive immediate-onset responses were observed. As a result of challenge with the respective conjugate of the hapten conclusive immediate-onset responses occurred. Additional evidence of a lung sensitizing potential was provided by the histopathological examination which revealed an increased eosinophilia of airways and lung associated lymph nodes as well as specific IgG1-antibody. Therefore, this study provides clear evidence that 1,6-hexamethylene diisocyanate is a respiratory sensitizer in the guinea pig bioassay.