Glutathione in induced sputum of healthy individuals and patients with asthma

Background-Glutathione is central to the antioxidant defences of the lung. The aim of this study was to determine whether sputum induction can be used for the measurement of glutathione in the respiratory tract. Methods-Saliva and induced sputum (3% NaCl, 20 minutes) samples were collec ted from 10 healthy individuals and 10 patients with stable asthma receivin g treatment with inhaled corticosteroids. Samples were chilled on ice and d ispersed by dilution with ice cold phosphate buffered saline and pipetting. Cell-free supernatants were obtained by centrifugation of samples and filt ration of supernatants and analysed for total glutathione, glutathione disu lfide, and albumin content. The cells were treated with dithiothreitol and cell numbers, cell viability, and differential cell patterns were determine d. Results-As judged by cell viability and percentage of non-squamous cells, a dequate sputum samples were obtained from nine healthy and nine asthmatic s ubjects. The salivary total glutathione content was low (median concentrati on 1.2 muM (range 0.8-1.5) in healthy subjects and 0.9 muM (0.7-1.2) in ast hmatic subjects). The sputum total glutathione content of both healthy and asthmatic subjects was within the same range (3.9 (1.0-12.3) muM and 6.4 (1 .3-19.2) muM, respectively; p=0.35). Surprisingly, and in marked contrast t o results obtained with bronchoalveolar lavage, sputum levels of glutathion e disulfide represented more than 50% of the total glutathione in both grou ps (50.9% (range 24.6-83.1) and 72.3% (range 36.5-97.4), respectively; p=0. 2). Conclusions-The results of this study indicate that sputum induction can be used to measure the glutathione content of bronchial secretions. Sputum gl utathione levels of stable asthmatic patients did not differ significantly from healthy controls.