A method for the long-term exposure of rabbits to environmental pollutant gases

The aims of the present study were twofold. Firstly, we wanted to develop a system for the exposure of rabbits to pollutant gases that would monitor gas concentrations accurately, allow flexibility, be simple to operate, and could be constructed at relatively modest cost. Additionally, we wanted to determine whether the procedures necessary for the daily exposure of young rabbits had any detrimental effect on their development. Using the environmental exposure system that we developed, littermate New Zealand White rabbits, neonatally immunized to either Alternaria tenuis or house dust mite antigen were exposed 2 h daily, from within 24 h of birth until 3 months of age, to either 4 ppm nitrogen dioxide (NO2), or 5 ppm sulphur dioxide (SO2) or ambient air. The environmental exposure system consists of four sections; a stainless steel exposure chamber; an airflow monitoring and control system and gas delivery system; a gas detector and monitoring system; and an exhaust fan. Equilibration and wash-out times of gas were short and the gas mixing within the chamber atmosphere was uniform. Levels of gases were reliably maintained throughout the period of exposure within predetermined limits. The weights of the immunized, gas-exposed animals did not differ significantly from those of the immunized, air-exposed animals at any time throughout the 3 month period of exposure. At 3 months of age, the basal values for lung resistance and dynamic compliance did not differ between gas- and air-exposed rabbits. These values did not differ significantly from those obtained from naive animals of the same age. Our results suggest that we have developed a sensitive, reliable and simple environmental exposure and monitoring system. It is anticipated that the methodology described will allow the careful investigation of the effects of long-term exposure to pollutant gases from birth on the development of airways hyperresponsiveness.