Background: The effect o f a specific protein kinase A inhibitor H89 on Aquaporin 5 (AQ5) levels, which has a role in the inflammation o f asthma pathogenesis, was investigated in this study. Objective: To prove that H89, which was thought to be a promising agent, may show antiinflammatory activity in the treatment o f asthma by causing inhibition o f the protein kinase A enzyme that is involved in inflammation. Methods: Thirty-two Wistar-Albino adult male rats, ranging between 250 and 350 g, were divided intofour groups: (a) control group; (b) sham group, administration o f1 ml ovalbumin -OVA) -olution intraperitonal -IP) and -.1 ml OVA dissolved -n dimethyl sulfoxide intranasally; (c) asthma group, IP + intranasally OVA administration; and (d) H89 group, (IP + intranasally OVA) + 0.1 ml H89. The lungs o fthe rats were evaluated histopathologically and immunohistochemically at the end of the study. Results: The histopathological changes and AQ5 levels o f the sham and asthma groups were not statistically different (p > 0.05). However, the parameters were found to be increased in the asthma group compared with the control group (p < 0.001). The alveolar degeneration and vascular congestion were statistically significantly decreased in the H89 group (p < 0.05). The AQ5 levels were reduced in the H89 group, but the difference was not statistically significant. Conclusion: Aquaporin 5 levels and histopathological changes were increased in asthmatic patients, -nd an -mprovement was detectedwith H89 -reatment. H89 has an -fleet on -he -nflammation of asthma pathogenesis, so it can be thought to be used in asthma treatment. However, more studies are needed tofind out the therapy duration and ideal doses o fH89 treatment.