Inhibition of pulmonary eosinophilia does not necessarily prevent the airway hyperresponsiveness induced by Sephadex beads.

Background: The Lewis rat among highly inbred strains exhibits significant airway hyperresponsiveness (AHR) following intravenous administration of Sephadex G-200 (Sephadex). The aim of this study was to investigate the association of Sephadex-induced AHR with changes in airway inflammation in Lewis rats.
Methods: A suspension (0.5 mg/ml/rat) of Sephadex was intravenously administered to male Lewis rats on days 0, 2 and 5. Measurement of airway responsiveness to serotonin, bronchoalveolar lavage (BAL) and histological study were performed on day 2-11.
Results: Significant AHR induced by Sephadex was recognized on day2 (p < 0.05), and AHR reached a maximum on day 7 (p < 0.001). In the BAL study, eosinophils increased on day2 (p < 0.01) with a peak on day 5 (p < 0.05). In the histological study, we found Sephadex beads trapped in small arteries of the lung and granulomatous arteritis on day 2 or later. Pulmonary granulomas, horseshoe-shaped multinuclear giant cells, eosinophils and goblet cell hyperplasia were observed on day 2, and the degree became intense on day 5-7. GCC-AP0341 (10 mg/kg, i.p. x 3) inhibited the recruitment of eosinophils in BAL fluid and in lung tissue, but it did not inhibit AHR. The compound also inhibited pulmonary granulomas and goblet cell hyperplasia.
Conclusion: The mechanism of Sephadex-induced AHR may not be directly associated with inflammatory changes such as recruitment of eosinophils, pulmonary granulomas and hyperplasia of goblet cells in rats.