Measurement of GSH-Px activity was based on the method described by Kaynar et al (13). The whole activity of GSH-Px was evaluated using the oxidation of glutathione (GSH) reacted with cumene hydroperoxide. In the presence of glutathione reductase and NADPH, the oxidized glutathione is immediately converted to the reduced form with a concomitant oxidation of NADPH to NADP+. The reduction in the absorbance of NADPH at 340 nm was measured. One unit of GSH-Px activity is defined as the amount of enzyme that catalyzes the oxidation of 1 μmol of reduced glutathione (GSH) by cumene hydroperoxide to oxidized GSH per min at pH 7.0 at 37˚C.