[Dose-effect relationship between vitamin C and
paraquat poisoning rats].

OBJECTIVE: To explore the dose-effect relationship between vitamin C and paraquat (PQ) poisoning rats.
 Methods: A total of 40 Sprague-Dawley (SD) rats were randomly divided into 4 groups: a control group, a PQ poisoning group, a vitamin C group 1 and a vitamin C group 2 (n=10 in each group). 150 mg/kg PQ was perfused into rat stomach to establish PQ poisoning rat model. In PQ poisoning group, 30 mg/kg methylprednisolone and 2.5 mg/kg cyclophosphamide were injected peritoneally on the basis of PQ poisoning rat model. In vitamin C1 and C2 group, vitamin C was injected at a dosage of 5 or 500 mg/kg, respectively. The control group only received normal saline (NS). The malondialdehyde (MDA), liver and kidney function as well as arterial blood gas in the blood were examined 36 h later. At the end, the rats were killed and took the liver tissues for pathological examination and weight ratio calculation. The glutathione peroxidase (GSH-PX), ctychrome C (Cyt C) in the liver tissues were detected by chromatometry, and the Bcl-2 was detected by Western blot.
 Results: Compared with the PQ poisoning group, the MDA and Cyt C were decreased, the GSH-PX was increased, and liver and kidney functions were improved in the vitamin C group 1 (all P<0.01); but in the vitamin C group 2, the MDA increased and liver/kidney functions were impaired (all P<0.01). The expression of Bcl-2 in the PQ poisoning group was lower than that in the control group; compared with the PQ poisoning group, it was increased in the vitamin C1 group, while it was decreased in the vitamin C group 2 (both P<0.01). There was no obvious difference in the lung function, wet/dry weight ratio and pathological changes between the poisoning group and experimental groups (all P>0.05).
 Conclusion: Vitamin C at the low dose shows a certain degree of protection for the liver and kidney in the PQ poisoning rats model through it antioxidative activity and anit-apoptosis activity, while vitamin C at the high does may promote oxidation. Meanwhile, vitamin C doesn't show protective effect on lung in the PQ poisoning rats.