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1 Servei de Pneumologia, Hospital Clínic, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Universitat de Barcelona, Barcelona, Spain, 2 Dept of Internal Medicine at Huddinge University Hospital and Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
CORRESPONDENCE: R. Rodriguez-Roisin, Servei de Pneumologia, Hospital Clínic, Villarroel, 170. 08036-Barcelona, Spain. Fax: 34 932275404. E-mail: rororo@clinic.ub.es
Keywords: Leukotriene inhalation challenge, leukotriene receptor antagonists, ventilation-perfusion mismatching
Received: December 23, 2004
Accepted May 10, 2005
Bronchoprovocation with cysteinyl-leukotrienes (LTs) induces airflow obstruction and gas exchange abnormalities, namely ventilation-perfusion ratio (V'A/Q') imbalance. However, it is unknown which of the two different receptors for cysteinyl-LTs mediate these V'A/Q' disturbances.
In a double-blinded, crossover design, 10 patients with mild asthma were randomised to receive an oral single dose of the selective cysteinyl-LT1 receptor antagonist montelukast (40 mg) or placebo before leukotriene (LT)D4 inhalation challenge. Gas exchange, including V'A/Q' descriptors were measured at baseline, 3 h after montelukast/placebo pretreatment and 5, 15 and 45 min after the LTD4 challenge.
Compared with montelukast, inhalation of LTD4 induced a marked fall in forced expiratory volume in one second (mean±SE 33±2%) and profound V'A/Q' mismatching, reflected by a decreased arterial oxygen tension (from 100±4 to 75±3 mmHg) and an increased overall index of V'A/Q' heterogeneity dispersion of retention minus excretion inert gases corrected for dead space (from 4.9±1.2 to 8.4±1.1; normal
In conclusion, these findings point to the view that leukotriene D4-induced gas exchange disturbances and bronchoconstriction are both mediated by the cysteinyl-leukotriene1 receptor.
3.0; dimensionless), 5 min after placebo. Following montelukast, LTD4 produced no significant changes in any of the variables.
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