Effects of folic acid on antioxidant enzyme,nitric oxide synthase and nitric oxide in ovariectomized rats

AIM: To observe the effects of folic acid (FA) on antioxidant enzyme, nitric oxide synthase (NOS) and nitric oxide (NO) in ovariectomized (OVX) rats.METHODS: Forty three-month-old female SD rats were randomly divided into 5 groups: sham group, OVX group, diethylstilbestrol group (0.03 mg·kg^-1·d^-1), low-dose FA group (5 mg·kg^-1·d^-1) and high-dose FA group (20 mg·kg^-1·d^-1). Gastric gavage started 1 week after operation and lasted for 10 weeks. The rats in sham group and OVX group were given distilled water instead of FA as controls. At the end of the 10th week, the L₅ vertebra and right femur were removed for determination of bone mineral density (BMD). The bone homogenates were made using the L₃ and L₄ vertebrae. The levels of the total antioxidant capacity (TAC), glutathione peroxidase (GSH-Px), malondialdehyde (MDA), NOS and NO were detected in plasma and bone homogenates.RESULTS: Compared with sham group, the BMD levels in L₅ vertebra and right femur and the levels of GSH-Px and NO in the plasma were all decreased. The levels of TAC, GSH-Px, NOS and NO in the bone homogenates were also decreased, while the MDA concentration was increased in OVX group (all P < 0.01). Compared with OVX group, the levels of TAC, GSH-Px, NOS, NO and BMD of the L₅ vertebra and right femur were all increased, while the MDA concentration was decreased in high-dose FA group (all P < 0.01). CONCLUSION: In female SD rats, ovariectomy leads to a significant reduction of antioxidant enzyme, NOS and NO levels. Oxidative stress is possibly involved in the development of osteoporosis. Protection against osteoporosis by high-dose FA may be linked to improvement of antioxidant enzyme activity, the levels of NOS and NO as well as a reduction of oxidative stress in ovariectomized rats.