Objective  To observe oxidative injury in brains of mice induced by high dose of phenylalanine (Phe).

  Methods  Forty healthy male C57 mice were randomly divided into four groups: high-, moderate-, and low-dose groups (with Phe of 4.20, 2.10, and 1.05 mmol/kg) and a control group (with double distilled water). Intragastric administrations were conducted once a day for 28 days. Twelve hours after the last intragastric administration, brain tissues of the mice were sampled for measurements of the activities of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), catalase (CAT), and the levels of malondialdehyde (MDA), glutathione (GSH), reactive oxygen species (ROS), and 8-hydroxy deoxyguanosine (8-OHdG).

  Results  The contents of ROS, 8-OHdG and MDA in brain tissues of the mice with Phe administration were all significantly lower than those in the brain tissues of the control mice (all P < 0.05). The contents of 8-OHdG in brain tissues of the mice with Phe administration increased significantly in a dose-dependent manner (0.41 ± 0.04, 0.29 ± 0.02, and 0.23 ± 0.02 ng/mL for high-, moderate-, and low-dose group) (all P < 0.05); while those of MDA decreased significantly also in a dose-dependent manner (2.10 ± 0.21, 2.75 ± 0.20, and 3.25 ± 0.31 nmol/mg pro for high-, moderate-, and low-dose group) (all P < 0.05). Compared with those of the control mice and the mice with moderate-, and low-dose Phe, the activities of SOD (71.72 ± 6.99 U/mg pro), GSH-Px (35.53 ± 3.18 U/mg pro), CAT (3.95 ± 6.30 U/mg pro) decreased obviously in brains of the mice with high-dose Phe (P < 0.05 for all). In comparison with that of the control mice, the GSH content decreased significantly in brain tissues of the mice with Phe, in a dose-dependent manner (2.55 ± 0.25, 3.45 ± 0.33, and 3.96 ± 0.34 mg/g pro for high-, moderate-, and low-dose group) (all P < 0.05).

  Conclusion  High dose of phenylalanie may not induce oxidative injury but might inhibit the oxidative metabolism in brain tissues of mice.