Ciliary Activity and Electron Microscopic Structure according to the Levels of Respiratory Tract in the Mouse, Rat and Guinea Pig

ABSTRACT

Few studies have attempted a systematic comparison of ciliary beat frequency (CBF) and ciliary ultrastructure across different species and different levels of the respiratory tract. The aim of this study was to observe the CBF and ciliary ultrastructure of mice, rats and guinea pigs according to varying sites of the respiratory tract. Balb/c mice, Wistar rats and Dunkin-Hartley guinea pigs were used. We measured CBF using a video-computerized analysis technique at the middle of the maxilloturbinal, the nasopharynx, the upper trachea and the main bronchus in vitro. Ciliary length and the proportion of ciliated epithelium were assessed with scanning electron microscopy (SEM). In the rat, CBF was lower in the main bronchus (9.7+/-0.4 Hz) than at other sites, but there was no difference in CBF values across different airway sites in mice and guinea pigs. The CBF in the main bronchus was higher in guinea pigs than in rats and mice. SEM showed that the cilia of the rat were significantly shorter in the upper trachea and the main bronchus than in the maxilloturbinal and the nasopharynx. The respiratory epithelia of guinea pigs were more ciliated than those of mice and rats, especially in the upper trachea and the main bronchus. The guinea pig may be a superior experimental animal for ciliary function studies because the guinea pig has a less variable CBF and more uniform distribution of ciliated cells along different levels of the airway. These results provide valuable data relevant to ciliary functional studies using animal models.