ABSTRACT
OBJECTIVE To establish secretory otitis media(SOM) model induced by endotoxin and evaluate its reliability. METHODS Healthy 50 Sprague-Dawley rats of either sex( 250-300g)were randomly divided into experimental group(ET group) and control group(NS group),with 30 and 20 rats respectively. 35ul volume of 1mg/ml endotoxin from Pseudomonas aeruginosa and same amount of saline(NS) were transbullaly injected into the right tympanic bullas of the two groups. Six rats of ET group and four rats of NS group were killed postoperative on 6h,1d,3d,7d,14d respectively. The temporal bones were harvested for histological study. The left tympanic bullas served as control. Another four rats(each group 2 rats) were used for SEM study with the same method. One rat was killed and harvested for SEM observation of mucocilliary transporting system on the tympanic ostium of Eustachian tube. RESULTS ①LM(light microscope):The epithelial layer and subepithelial space(SES) were thicked mildly in ET group at 6 hours,and more heavily at 1 day with inflammatory cells infiltration (mostly polymorphonuclear leukocytes,PMNs). At 3 days,the same changes were observed most severely. By 14 days,the mucosal lining returned to normal. No obvious changes were observed in the NS group. ②SEM(scan electrical microscope):In ET group,the impairment of mucociliary transport system such as lodging,shedding of cilias were observed at 3 days and returned to normal at 14 days. No abnormal changes were observed in NS group. CONCLUSION Endotoxin can induce SOM with inflammatory changes peak at day 3 and return to normal by day 14.