The Effect of Methylene Blue on Nitric Oxide Production in a Rat Model of Acute Liver Injury Induced by Paraquat

ABSTRACT

PURPOSE: This study was to investigate if methylene blue (MB) inhibited lipid peroxidation, nitric oxide (NO) generation, and gene expression of iNOS in acute liver injury induced by paraquat and if the inhibitory effect of MB was dose dependent. METHODS: Female Sprague-Dawley rats were divided into four groups the control group, the group treated only with paraquat, and the groups treated with paraquat and low or high dose of MB (2 mg/kg, 20 mg/kg). RESULTS: The liver histology, the malondialdehyde (MDA) level, and the NO concentration in blood and the expression of iNOS mRNA in liver tissue were measured. The liver histology showed decreased inflammatory responses in the MB-treated groups compared to the group treated with paraquat only. The amount of liver MDA decreased in the MB-treated groups compared to the paraquat-only-treated group. There was a significant decrease in the MDA level in the high-dose MB-treated group. The plasma NO concentration decreased more in the MB-treated groups (low and high) than in the paraquat-only-treated group. There was a significant decrease in the plasma NO concentration at 6 h in the high-dose MB-treated group. Gene expression of iNOS mRNA in the liver tissue was slightly lower in the MBtreated group than in the paraquat-only-treated group. CONCLUSION: In this study, MB had an the antioxidant effect and an inhibitory effect on the plasma NO concentration and the expression of iNOS mRNA in the liver. The inhibitory effect of MB was dose dependent.