Abstract: AIM: To observe the effect of budesonide on the expression of inducible nitric oxide synthase (iNOS) at blood polymorphonuclear leukocyte (PMN) in asthma rats. And to approach the pathogenesis of PMN in asthma inflammation. METHODS: The model rats of asthma were induced by OVA and Al (OH) 3.The blood PMN was isolated and purified. The expressions of iNOS protein at blood PMN were detected by immunohistochemical method. The concentration of nitric oxide (NO) at bronchoalveolar lavage fluids (BALF) were detected by colorimetric method. RESULTS: Expressions of iNOS protein at PMN in asthma group were significantly higher than those in control group (P <0.01). And the expressions of iNOS protein at PMN in budesonide treated group were significantly lower than those in asthma group (P < 0.01). The expressions of iNOS protein at bronchial wall in asthma group were significantly higher than those in control group (P <0.01). And the expressions of iNOS protein in budesonide treated group were significantly lower than those in asthma group, but higher than those in control group (all P <0.01). Concentrations of NO at BALF in asthma group were significantly higher than those in control group (P < 0.01). Concentrations of NO at BALF in budesonide treated group were significantly lower than those in asthma group. There was significant positive correlation between the expressions of iNOS protein at blood PMN and NO concentration at BALF(n =29, r =0.754, P <0.01). And there was significant positive correlation between the expressions of iNOS protein at bronchial wall and NO concentration at BALF (n =29, r = 0.760, P <0.01). CONCLUSION: The levels of iNOS protein synthesized by PMN are increased in asthma rats. PMN may be implicated with asthma pathogenesis via iNOS, but this function of PMN can be partly inhibited by budesonide.

Key words: asthma, inducible nitric oxide synthase, nitric oxide, polymorphonuclear leukocyte, rat