Lung clearance of particles in two strains of rats

Two strains of commonly used experimental rats were compared with regard to lung clearance of TiO2 particles. The Fisher 344 inbred rats retained predictably fewer particles after a 7-hr exposure than the larger outbred Long-Evans rats. This fact can be expected in view of the different lung size of the two strains. In addition, clearance of the retained particles was significantly slower in Fisher 344 rats. Differences in lung clearance capacity of different animal strains should be considered when experiments in inhalation toxicology are performed.