Ciliary ultrastructure and beating activity in rat and guinea-pig respiratory mucosa

1. The rat and the guinea-pig are commonly used animals when the effects of drugs on ciliary activity in respiratory airways are studied. There are few data concerning the possible differences in ciliary function between these two animals. 2. Using a photodetector method we measured the ciliary beating frequency (CBF) from the upper part of the trachea, the lower part of the trachea and the distal part of the main bronchi (subsegmental bronchi) of rat and guinea-pig respiratory tract. In addition, the structure of the cilia was studied using scanning electron microscopy (SEM). 3. CBF in the rat respiratory tract was significantly lower than in the guinea-pigs. In the upper trachea, the CBF for rat was 12.7 beats/s and 15.3 beats/s for guinea-pig. The respective values were 9.2/16.0 beats/s in the lower part of the trachea and 6.9/13.8 beats/s in subsegmental bronchi. In both rats and guinea-pigs CBF was lower in the subsegmental bronchi than in the trachea (rat: 25.0-45.7%, guinea-pig: 9.8-13.8%). 4. In addition to higher CBF, the quality of the photo-electrical signal was better from guinea-pig tissues, probably as a result of the larger amounts of ciliated cells and longer cilia of guinea-pig respiratory epithelial compared to those in rat mucosa. 5. SEM showed that the rat cilia were on average shorter (3.6 vs 4.3 microns) and thinner (0.19 vs 0.22 microns) than those of the guinea-pig. Rat mucosa was markedly less ciliated than the respiratory mucosa of the guinea-pig.(ABSTRACT TRUNCATED AT 250 WORDS)