Objective:To study the effects of intranasal FP on the expression of AQP5 in epithelial cells of nasal mucosa and nasal polyps and further explore the possible mechanism of AQP5 in the onset of nasal polys. Methods:The primary culture of the epithelial cells of nasal mucosa was conducted for 14 days. After these cells were subcultured.The cells of FP group was treated with culture medium containing 0.2% FP.The cells of no FP group were treated with culture medium which was not containing FP. After 7 days,the expressions of AQP5 were studied in the cells with immunohistochemistric staining,by its integrated light intensity and its grey step. At the first day we obtain 12 nasal polyps samples from these inpatients who were trouble with chronic sinusitis and nasal polyps for the first time and were not treated with glucocorticoid partly or integreatly in the last three mouths. FP were intranasally used 7 days before operation.The other 12 nasal polyps were obtained and studied with immunohistochemical technique,by its light intensity and its grey step. Results:The grey step of AQP5 in the cells of FP-using group is lower obviously than using FP before(P < 0.05),the light intensity is higher obviously than using FP before(P < 0.05). In the nasal polyps of FP-using group,the size of nasal polyps become much smaller than using FP before.The grey step of AQP5 in both glandular cells and lymphocyte is higher obviously than using FP before(P < 0.05) but the light intensity is lower obviously than using FP before(P < 0.05). Conclusion:the expressions of AQP5 in cells which treated with FP became higher than cells which untreated,It indicated that when treated with FP,interstitial fluid can effuse easily,the concha nasalis media and the concha nasalis inferior became smaller and smaller. After nasal polyps samples treated with FP,the poloyps became smaller.At the same time,the expressions of AQP5 in glandular cells and lymphocyte became lower. There may be relationship between these. It can indicate that AQP5 contributed to edema of nasal polyps.