SOD1 and holoprosencephaly: MTX administration significantly decreased the antioxidant enzyme activities of CAT (45.6 ± 0.35) (Fig. 3C) and SOD (4.48 ± 0.91) (Fig. 3D) in liver tissues in comparison with the control group, but data show a marked increase (p < 0.001) in tissue concentrations of CAT (85.4 ± 6.26) and SOD (7.94 ± 0.69) activity in liver tissues post exposure to HPE as compared with the MTX group.