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Cattedra di Fisiopatologia Respiratoria, Dipartimento di Scienze Motorie e Riabilitative, and Cattedra di Biochimica, Dipartimento di Medicina Sperimentale, Università di Genova, 16132 Genoa, Italy
We studied the
intracellular mechanisms of allergen-induced
2-adrenoceptor dysfunction in human isolated passively
sensitized bronchi. Sensitization was obtained by overnight incubation
of bronchial rings with serum containing a high specific IgE level to
Dermatophagoides but a low total IgE level. Allergen
challenge was done by incubation with a Dermatophagoides
mix. The Gs protein stimulant cholera toxin (2 µg/ml) displaced the carbachol (CCh) concentration-response curves of
control and sensitized but not of challenged rings to the right.
Cholera toxin (10 µg/ml) displaced the concentration-response curves
to CCh of control, sensitized, and challenged rings to the right, but
this effect was less in challenged rings. The effects of the
Gi protein inhibitor pertussis toxin (250 ng/ml or 1 µg/ml) on salbutamol concentration-relaxation curves did not differ
significantly between challenged and sensitized rings. The adenylyl
cyclase activator forskolin and the Ca2+-activated
K+-channel opener NS-1619 relaxed CCh-contracted bronchial
rings without significant differences between control, sensitized, and challenged rings. Neither Gi nor Gs
-subunit
expression differed between control, sensitized, and challenged
tissues. We conclude that Gs protein dysfunction may be a
mechanism of allergen-induced
2-adrenoceptor dysfunction
in human isolated passively sensitized bronchi.
airway smooth muscle; calcium-activated potassium channels; adenylyl cyclase; Gi protein;
-adrenergic receptors
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