SOD1 and cystic fibrosis: Melatonin promoted the activation of the antioxidant enzymes in fresh embryos (6.7 vs. 5.1 μM GST/embryo, and 2.1 vs. 0.7 units SOD/embryo in MF vs. CF groups, respectively, P<0.05) and in vitrified embryos (6.3 vs. 4.3 μM GST/embryo, and 1.7 vs. 0.6 units SOD/embryo in MV vs. CV groups, respectively, P<0.05).