AN AUTOMATED-SYSTEM FOR ANIMAL EXPOSURE TO NITROGEN-DIOXIDE

We have designed an automated system for controlled exposure of rodent s to nitrogen dioxide (NO2). The system consists of 1) two stainless-s teel exposure chambers (3.96 m(3)), for control and treated animals, i n which temperature, humidity, and air changes are consistent with cur rent guidelines for rodent housing; 2) a cylinder containing 1% NO2 in N-2; 3) a detector connected with a personal computer system that mon itors the NO2 concentration, and regulates the NO2 influx, using a clo sed-loop feedback; and 4) a fan system to distribute the gas uniformly within the chambers. In a typical experiment rats were exposed to 15 ppm of NO2, and changes in the differential count of polymorphonuclear leukocytes, macrophages, and lymphocytes in bronchoalveolar lavage fl uid were investigated.