OVA-sensitized mice were sacrificed on day 21 by enflurane overdose, exsanguinated, and their lungs were removed. The main bronchi were rapidly dissected and cleaned from fat and connective tissue. Rings of 1–2 mm length were cut and mounted in 3 mL isolated organ baths containing Krebs solution, at 37 °C, oxygenated (95% O2 and 5% CO2), and connected to an isometric force transducer (type 7006, Ugo Basile, Comerio, Italy) associated to a Powerlab 800 (AD Instruments, Oxford, UK). Rings were initially stretched until a resting tension of 0.5 g was reached and allowed to equilibrate for at least 30 min during which tension was adjusted, when necessary, to 0.5 g and the bathing solution was periodically changed. In each experiment, bronchial rings were previously challenged with carbachol (1 × 10−6 M) (Sigma-Aldrich, Milan, Italy) and then a cumulative concentration-response curve of carbachol (1 × 10−9 M − 3 × 10−6 M) or salbutamol (1 × 10−8–3 × 10−5 M) was performed to evaluate bronchial reactivity. Results are expressed as dyne per mg tissue [37 (link),38 (link)].
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