INTRATRACHEAL INHALATION VS INTRATRACHEAL INSTILLATION - DIFFERENCES IN PARTICLE EFFECTS

Our laboratory has developed a method of intratracheal inhalation wher eby rats can be exposed to high aerosol concentrations, resulting in h igh lung particle burdens in a short time period with deposition occur ring directly in the lower respiratory tract, thus avoiding many drawb acks of larger nose-only or whole body inhalation systems. In this rep ort, we compare the response of rats exposed by intratracheal inhalati on to ''fine'' (similar to 250 nm) and ''ultrafine'' (similar to 21 nm ) titanium dioxide particles with rats exposed to similar doses by int ratracheal instillation. Animals receiving particles through inhalatio n showed a decreased pulmonary response, measured by bronchoalveolar l avage parameters, in both severity and persistence, when compared with those receiving particles through instillation. These results demonst rate a difference in pulmonary response to an inhaled vs an instilled dose, which may. be due to differences in dose rate, particle distribu tion, or altered clearance between the two methods. (C) 1997 Society o f Toxicology.