Salbutamol pretreatment does not change eosinophil percentage and eosinophilic cationic protein concentration in hypertonic saline‐induced sputum in asthmatic subjects

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Abstract
Background    Sputum induction by inhalation of hypertonic saline (HS) is usually preceded by β2‐agonist pretreatment, to prevent severe bronchoconstriction. Objective    To evaluate whether salbutamol pretreatment may influence cell counts and concentrations of soluble mediators in induced sputum. Methods    We studied 22 patients who randomly underwent HS sputum induction after pretreatment with either 200 μg salbutamol or placebo. Sputum was induced by means of HS inhalation (3, 4, 5% NaCl, 10 min each), measuring FEV1 every 5 min until it fell ≥ 20% from baseline. Collected sputum was diluted 1 : 1 with 0.1% DTT, incubated at 37 °C for 20 min, and total and differential cell counts were measured. ECP and histamine levels were measured in the supernatant. Results    Sputum volume, percentages of inflammatory cells, squamous cell counts and quality of the slides were not different after the two pretreatments, while sputum total inflammatory cells after salbutamol tended to be higher than after placebo (8.3 [1–41] ×106 vs 6.3[0.2–40] ×106; P = 0.09). Eosinophilic cationic protein (ECP) did not significantly change (260 [8–900] μg/L after salbutamol vs 200 [8–800] μg/L, n = 19), while histamine levels tended to be lower after salbutamol (140.9 [39.9–236.5] n m) than after placebo (190.4 [72.2–322.6] n m, P = 0.09, n = 17). The airway response to HS inhalation was significantly greater after placebo and the duration of the test was significantly different (median: 15 min after placebo and 30 min after salbutamol). Similar results were obtained when patients who differed for more than 15 min in the duration of HS‐inhalation in the two tests were selected (n = 11). Conclusion    Salbutamol pretreatment reduces the severity of bronchoconstriction induced by HS inhalation without significantly affecting the percentages of inflammatory cells and the levels of soluble mediators in induced sputum.

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