CFTR and cystic fibrosis: In addition to CFTR permeability for GSH, polymorphisms in regulatory genes of the metabolic pathway of GSH were associated with different phenotypes of CF and its severity (Linsdell and Hanrahan, 1998; Hudson, 2001; Jungas et al., 2002; Marson et al., 2013; Marson et al., 2014).