MUC5AC and chronic obstructive pulmonary disease: As cigarette smoking (CS) is the leading cause of COPD [14] and tracheal goblet cell hyperplasia as well as bronchoalveolar lavage fluid (BALF) mucin remained significantly elevated even when the rats were exposed to five cigarettes daily for 2 to 4 days [15], the current study was to investigate the effect of hydrogen-rich saline on CS-induced mucus production in rats.