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 deve lop a system for the exposure of rabbits to pollutant gases that would monitor gas concentrations accurately, allow flexibility, be simple t o operate, and could be constructed at relatively modest cost. Additio nally, we wanted to determine whether the procedures necessary for the daily exposure of young rabbits had any detrimental effect on their d evelopment. 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, f rom within 24 h of birth until 3 months of age, to either 4 ppm nitrog en dioxide (NO2), or 5 ppm sulphur dioxide (SO2) or ambient air. The e nvironmental exposure system consists of four sections; a stainless st eel 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 m ixing within the chamber atmosphere was uniform. Levels of gases were reliably maintained throughout the period of exposure within predeterm ined 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 sam e age. Our results suggest that we have developed a sensitive, reliabl e and simple environmental exposure and monitoring system. It is antic ipated that the methodology described will allow the careful investiga tion of the effects of long-term exposure to pollutant gases from birt h on the development of airways hyperresponsiveness.