Effect Of Methylene Blue On Lung INOS Expression And Lung Injury Of Septic Rats In Different Periods

Objective: To investigate the effect of methylene blue on the expression of iNOS in lung of different periods of sepsis, and whether it can reduce the lung injury. Methods:The model was established by cecal ligation and puncture(CLP). 140 Wistar female rats were randomly divided into 0, 6, 12, 18, 24, 30, 36 h group according to the time of administration, All rats were intravenously injected 15 mg/kg methylene blue(MB),and observation for 120 hours. 126 female Wistar rats were randomly divided into 0, 6, 12, 18,24, 30, 36 h groups. Each group was divided into sham group, CLP group and methylene blue group three subgroups. Methylene blue group was injected 15 mg/kg MB after CLP 0、6、12、18、24、30、36 h, respectively. Remaining rats were given the same doses of 0.9%NaCl solution. After administration of 6 h, measuring rat blood pressure, artery blood gas.Collection of blood and the rats were sacrificed and the lung tissue was harvested immediately. Serum NO level was detected by nitrate reduction method. The lung tissues were determined the expression of iNOS protein by Western Blot, and the expression of iNOS mRNA by real-time quantitative polymerase chain reaction(qRT-PCR). Lung tissue were tested by histopathology. Result: The survival rate of septic rats was statistically significant in each group after operation(P<0.01); The survival rate of 0~24 hour was significantly lower than that of 30~36 hour. The median survival time of sepsis rats increased gradually after 24 h, and the survival rate increased gradually. With the time prolonged, MAP and phenylephrine responsiveness of CLP rats decreased(P< 0.05). MB significantly improve the operation after 12 h of sepsis rats mean arterial pressure, and improve the 12~30 h vascular reactivity of phenylephrine(P < 0.05). The level of serum NO was increased in CLP rats after operation, MB significantly decreased serum NO level(P < 0.05). The lactic acid concentration in the CLP group increased gradually with the time of operation, and the lactic acid in the methylene blue group was lower than that inthe sepsis group(P < 0.05). The expression level of iNOS gene and protein in lung tissue was different in different periods of sepsis, and the effect of MB on it was also different.In the early postoperative period, there was a lung tissue damage, which was more obvious in the late stage, and the effect of MB treatment on lung tissue injury was not significant. Conclusion: MB inhibited the expression of iNOS, reduces the concentration of nitric oxide(NO), maintains stable hemodynamics of rats with sepsis, and improves the reactivity of vasoactive drugs, but MB could not reduce lung injure.MB could significantly prolong the median survival time and survival rate of rats in late phase of sepsis, but had little effect on the early phase of sepsis.