GR was assayed according to the method of Foyer and Halliwell [30] by following the decrease in absorbance at 340 nm caused by NADPH oxidation (E = 6.2 mM cm−1). The reaction mixture consisted of 25 mM HEPES buffer (pH 7.8), 0.5 mM glutathione disulphide (GSSG), 0.12 mM NADPH, and the enzyme aliquot