Abstract

Bronchial rings from nonatopic humans were passively sensitized with serum from allergic subjects. Allergen challenge significantly reduced the relaxant effect of salbutamol on carbachol-induced contractions, suggesting beta(2)-adrenoceptor (beta(2)-AR) pathway dysfunction. Incubation of challenged rings for 3 h with 3 x 10(-6) M beclomethasone dipropionate (BDP) restored the relaxant effect, suggesting reversal of beta(2)-AR pathway dysfunction. Incubation with the G(s)alpha protein-stimulating cholera toxin attenuated contractile responses to carbachol significantly less in challenged than in unchallenged rings. Treatment of challenged rings with BDP resulted in an inhibitory effect of cholera toxin that was similar to the effect in unchallenged rings. G(s)alpha protein expression was not significantly altered by BDP, suggesting that the activity of G(s)alpha protein was increased. Relaxation of challenged rings by forskolin was not significantly affected by BDP, suggesting that beta(2)-AR pathway dysfunction was proximal to the adenylyl cyclase. In conclusion, short-term (3-h) treatment with BDP after allergen challenge ablated beta(2)-AR pathway dysfunction by increasing the activity of the G(s)alpha protein in human isolated bronchi.