Serious damage to the tracheal epithelium due to bronchoalveolar lavage (BAL) was recorded. Immediately after BAL 99 ± 2% of goblet cells were exhausted and degenerated. Their regeneration began 24 h after BAL resulting in hyperplasia of goblet cells with the formation of endoepithelial mucous glands. The most pronounced injury to the ciliated cells was apparent 2 h after BAL. BAL markedly impaired the ciliary border. The mean number of cilia/µm² fell to 1.5 ± 0.3/µm², then gradually rose to 7.5 ± 0.5/µm² (controls 9.7 ± 0.5/µm²). The morphological signs of impairment of the self-cleaning ability of the epithelium were the most pronounced after 24 h and were still present at the end of the experiment

Numerous signs of pathological alteration were induced in the pseudostratified ciliated epithelium by a 2-hour exposure to 90% oxygen. The ciliary border injury was especially conspicuous, the mean number of cilia in a given area was significantly (p < 0.005) reduced and morphological signs of impaired self-cleaning ability were revealed. Ciliated cells were severely injured showing apical blebbing and swelling of cell organelles. The reaction of goblet cells to exposure to O₂ was rapid discharge of mucus, but the mechanism of mucus evacuation was not substantially influenced. At the ultra-structural level, only a mild effect of humidification of the oxygen was observed

The effect of the application of a single oral dose of 100 mg of three mucolytic agents (N-acetylcysteine, carbocysteine and Na-2-mercaptoethane sulphonate) on the ultrastructure of the tracheal epithelium of healthy rabbits was studied. Due to the function of oral mucolytics the goblet cells were overstimulated and injured. Na-2-mer captoethane sulphonate was the least irritating substance. Acetylcysteine produced the most pronounced injury of the goblet cells, followed by rapid differentiation of these cells. Oral administration of all mucolytics studied caused local impairment of mucus flow in the airways.