Comparison of Responses of Respiratory System to Cigarette Smoke Inhalation between Brown Norway and Fischer 344 Rats

Abstract

Brown Norway (BN) rats are known to be hypersensitive to inhaled allergen or ozone. We compared the histological responses of the respiratory system following 2-week-inhalation of cigarette smoke between BN and Fischer 344 (F344) rats which have been widely used in long-term toxicity studies. F344 rats showed salivation and/or palpitation after every cigarette smoke-exposure while BN rats showed no clinical signs. Histologicaly, in the nasal mucosa near the open air, mild stratification of epithelial cells was seen in both strains. In the epiglottis, apparent stratification of hypertrophic epithelial cells was found in BN rats while squamous metaplasia with a distinct keratinized layer of mucous epithelium was observed in F344 rats. The number of alveolar macrophage in F344 rats was larger than that in BN rats. Serum VA level which is known to control epithelial cell differentiation did not show significant change by cigarette smoke challenge. These results suggest that the responses of the respiratory system were severer in F344 rats than in BN rats.