Mediators in Exhaled Breath Condensate after Hypertonic Saline Challenge

Abstract

Background. Airway narrowing after hypertonic saline challenge (HSC) is postulated to be mediated by bronchoconstrictors and inflammatory mediators. Objective. To study the mechanism of this challenge by using exhaled breath condensate (EBC). Methods. Fifty-six subjects (9 to 72 years of age) performed an HSC, with EBC collection and exhaled nitric oxide (FENO) measurements before and after the challenge. Bronchial hyper-reactivity (BHR) was defined if forced expiratory volume in 1 second (FEV₁) decreased by 10% compared with baseline (PD₁₀). EBC volume was recorded and was analyzed for mucin, histamine, nitrite/nitrate, and pH. Results. Those with BHR had a significant rise in EBC volume/5-minute collection period after challenge (286.3 ± 25.6 μl vs 402.2 ± 31.3 μl, p = 0.0002), while BHR(−) subjects did not show this change (387.6 ± 29.7 μl vs 364.1 ± 30.1 μl, p = 0.55). FENO showed a significant decrease in both BHR(+) and BHR(−) groups after challenge (p = < 0.0001). In BHR(+) subjects histamine increased significantly (1.3 ± 0.1 μM vs 1.5 ± 0.1 μM, p = 0.006) compared with baseline, while EBC pH and mucin increased significantly after HSC in both groups. EBC nitrite did not change in either group. Conclusion. EBC analysis suggests that HSC causes an increase in pH and mucin in both groups, but EBC volume and histamine only increased in the BHR(+) group. This suggests that mast cells are activated and fluid flux is associated with the positive response, while mucin release is independent of BHR in HSC.

Keywords :

• bronchial hyperresponsiveness
• mast cells
• histamine