Eucapnic hyperventilation-induced bronchoconstriction in rabbits.
We examined whether eucapnic hyperventilation with dry air produces the bronchoconstriction in anesthetized, non-sensitized rabbits and in ovalbumin sensitized rabbits. Eucapnic hyperventilation challenge with dry air containing 5% CO2 at room temperature was performed with 4 non-sensitized and 7 sensitized rabbits by mechanical ventilation for 15 min (120 breaths/min, 7 ml tidal volume/kg body weight). Total lung resistance (RL) and dynamic compliance (Cdyn) were measured before and 0, 5, 15, and 30 min after hyperventilation. In non-sensitized rabbits, RL and Cdyn did not change significantly. However, in sensitized rabbits, RL increased maximally by 48.9% +/- 9.0% at 5 min, and then decreased to the baseline level at 30 min after challenge. Cdyn decreased maximally by 12.5% +/- 3.5% at 15 min after challenge. These changes were significantly different from the baselines (p < 0.05). Furthermore, to investigate the role of histamine on hyperventilation-induced bronchoconstriction (HIB) in sensitized rabbits, we performed the hyperventilation challenges in 5 sensitized rabbits with the pretreatment of H1-receptor antagonist (chlorpheniramine, 1 mg/kg, i.v.) and found that the maximum increment of RL was suppressed to 24.2% +/- 7.4% of the control, which was significantly lower than the maximal RL in nontreated sensitized rabbits (p < 0.05). We concluded that HIB occurs only in sensitized rabbits and that histamine may play an important role in the development of HIB in sensitized rabbits.
Koyama
S
S
First Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan.
Ohtsuka
A
A
Horie
T
T
D000403:Airway Resistance / Q000502:physiology; D000818:Animals; D016084:Bronchoconstriction / Q000502:physiology*; D002245:Carbon Dioxide / Q000378:metabolism; D002744:Chlorpheniramine / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology; D006967:Hypersensitivity / Q000503:physiopathology; D006985:Hyperventilation / Q000503:physiopathology*; D008170:Lung Compliance / Q000502:physiology; D008297:Male; D010047:Ovalbumin / Q000276:immunology; D005082:Physical Exertion / Q000502:physiology; D011817:Rabbits
D002245:Carbon Dioxide; D002744:Chlorpheniramine; D006632:Histamine; D010047:Ovalbumin