Abstract: Objective: To investigate the dynamic changes of pulmonary morphology and mast cell activity in the rats after tracheotomy and intubation and their significances, and to elucidate the mechanism of occurrence of pulmonary inflammation in the rats after tracheotomy and intubation.Methods: A total of 48 SPF female SD rats were randomly divided into normal control group and tracheotomy and intubation group (n=24).The lung tissue and alveolar lavage fluid of the rats were collected at 24, 48, 72 and 168 h after modeling, respectively. The pathological changes of lung tissue of the rats were observed by light microscope. Transmission electron microscope was used to observe the mast cell ultrastructures of the rats. The levels of histamine, TNF-α and IL-6 in alveolar lavage fluid of the rats in two groups were measured by ELISA. The expression levels of β-tryptase in lung tissue of the rats in two groups were measured by immunohistochemical method.Results: The different levels of inflammation of lung tissue of the rats were found in tracheotomy and intubation group under light micscope and the Smith scores were higher than those in control group(P<0.05);the damage in tracheotomy and intubation group was aggravated with the prolongation of time, and the Smith scores were increased, there were significant differences between different time points (P<0.05).The mast cell degranulation at different levels of the rats in tracheotomy and intubation group were found at different time points, especially at 24 h. The histamine levels in alveolar lavage fluid of the rats in tracheotomy and intubation group at 24,72,and 168 h were higher than those in normal control group(P<0.05);there was no significant difference in the histamine levels at 48 h between two groups(P>0.05). The levels of TNF-a and IL-6 in alveolar lavage fluid of the rats in tracheotomy and intubation group at different time points were higher than those in normal control group (P<0.05);they reached a peak at 24 h and then declined(P<0.05).The expression levels of mast cell β-tryptase in the lung tissue of the rats in tracheotomy and intubation group at different time points were higher than those in normal control group(P<0.05), and reached a peak at 24 h(P<0.05).Conclusion: The lung mast cell activity is enhanced obviously after tracheotomy and intubation. It may be one of the main mechanisms of complicated pneumonia of the rats with tracheotomy and intubation.

Key words: tracheotomy and intubation, mast cells, inflammation, SD rats