Intratracheal Inhalation vs Intratracheal Instillation: Differences in Particle Effects

Our laboratory has developed a method of intratracheal inhalation whereby rats can be exposed to high aerosol concentrations, resulting in high lung particle burdens in a short time period with deposition occurring directly in the lower respiratory tract, thus avoiding many drawbacks of larger nose-only or whole body inhalation systems. In this report, we compare the response of rats exposed by intratracheal inhalation to “fine” (∼250 nm) and “ultrafine” (∼21 nm) titanium dioxide particles with rats exposed to similar doses by intratracheal instillation. Animals receiving particles through inhalation showed a decreased pulmonary response, measured by bronchoalveolar lavage parameters, in both severity and persistence, when compared with those receiving particles through instillation. These results demonstrate a difference in pulmonary response to an inhaled vs an instilled dose, which may be due to differences in dose rate, particle distribution, or altered clearance between the two methods.