Abstract
The pathogenetic trigger of bronchial asthma is airway hypersensitivity. Beclomethasone dipropionate (BDP), an adrenal cortical steroid preparation for inhalation, has been reported to suppress airway hypersensitivity. This study was designed to investigate the mechanism of this suppression of airway hypersensitivity in guinea pigs.
Using a whole-body exposure type inhalator equipped with a nebulizer of 38 liters capacity which pernuits puffing for 2 seconds, the animals were treated at a dose of 20 or 40 puffs a day (equivalent to a human dose of 600 or 1200μg/day, respectively), for 3 or 7 successive days. Airway hypersensitivity was assessed by the standard testing method of acetylcholine inhalation. Respiratory resistance was measured as an index representing the threshold of airway hypersensitivity. With 20puffs/day for 7 days, airway hypersensitivity tended to decrease. With 40 puffs/day for 3 days, it decreased more significantly (P<0.05). With 40 puffs/day for 7 days, it decreased with still significance (P<0.01).
Histamine levels in plasma and BALF significance (P<0.05) decreased after 7 days treatment at 40puffs/day. BDP seemed to inhibit airway hypersensitivity dependent upon and the number of days of inhalation as a result of the suppression of the mast cell-histamine chain. In addition, the drug tended to suppress capsaicin-stimulated airway hypersensitivity. The above results suggested that BDP suppresses airway hypersensitivity mediated by neuropeptides, especially by substance P.
