Effects of different concentrations of dexamethasone on pulmonary histology in rats with chronic asthma

Objective:To observe the intervention effects of different concentrations of dexamethasone on the general situation and pulmonary histology of chronic asthma rats,and to explore the suitable intragastric dose of dexamethasone in the rat model of chronic asthma.Methods:75 healthy male Sprague-Dawley(SD)rats were randomly divided into normal group,M group,dexamethasone low dose,middle dose and high dose group by random number table.The rat model of chronic asthma was established by sensitization and challenge of ovalbumin(OVA).From the 20th day of the experiment,dexamethasone groups were given intragastric administration of 0.0625mg/(kg·d),0.125mg/(kg·d)and 0.5mg/(kg·d),respectively.The general situation of rats was observed and recorded.The histological changes of rat lungs were observed by HE staining and Masson staining.Results:The degree of inflammatory infiltration of bronchus and surrounding tissue in the M group was significantly higher than that in the normal group(P<0.01).The thickness of airway wall and smooth muscle and the deposition of airway collagen in the M group were significantly higher than those in the normal group(P<0.01).After one week of intervention,the average daily food intake and body mass of rats in the high dose group were significantly lower than those in the M group(P<0.01),and the increase in body mass in the middle and low dose groups was significantly slower than that in the M group(P<0.01).After 2 weeks of intervention,the average daily food intake of rats in the middle and low dose groups was significantly lower than that in the M group(P<0.01).After 4 weeks of intervention,the average daily food intake in the middle and low dose groups was significantly lower than that in the low dose group(P<0.01).The inflammatory infiltration of lung tissue in the middle and low dose groups was significantly less than that in the model group,and the thickness of airway wall and smooth muscle and the deposition of airway collagen in the middle and low dose groups were significantly lower than those in the model group(P<0.01).There was no difference between the two groups(P>0.05).A large number of rats in the high dose group died after 5 times of intervention.Three rats died in the DEXM group at the 5th week of intervention,and there was no death in the other group.Conclusion:Both middle and low doses of dexamethasone can be used as the positive control dose in the experiment of chronic asthmatic rats,but the late side effects of low dose of dexamethasone are less,so the low dose of dexamethasone may be a safer and more suitable dose for the experiment of chronic asthmatic rats.