Background: Erythromycin showed an inhibitory effect on neutrophil exudation to the middle ear cavity in a rat model of otitis media.
Methods: Erythromycin (EM) was administered intraperitoneally into male Splague-Dawley rats at 10 mg/kg once daily for 7 or 14 days. A purified neutrophil suspension was employed in the neutrophil chemotaxis experiment using the Boyden chamber method.
Results: A significant increase in migration was observed at 50 and 100 ng/ml growth-related gene product (GRO) as compared to the assay with the addition of serum alone. Strong migration activity was also seen in the presence of zymosanactivated C5a in the assay medium. Treatment with EM for both 7 and 14 days suppressed the enhanced migration of neutrophils induced by 50 and 100 ng/ml GRO. In contrast, C5a significantly enhanced neutrophil migration under the treatment of EM for both 7 and 14 days.
Conclusion: The present study first revealed that EM administration to animals selectively inhibited the GRO-induced migration of neutrophils, which may contribute to its antiinflammatory effect on the upper respiratory mucosa.