The protective effect of melatonin pre-and post-treatment on experimental acute necrotizing pancreatitis with L-arginine-induced in rats

Objective To assess the protective effect of melatonin pre-and post-treatment on experimental acute necrotizing pancreatitis(ANP)with L-arginine(L-Arg)-induced in rats.Methods Ninety-six Spraque-Dawley male rats were randomly divided into four groups C,A,M1 and M2.ANP were induced by intraperitoneally injecting three times with 6% L-Arg at a dose of 25 mL/kg body weight at an interval of 1 h in group A.Group C received normal saline alone with the same methods.Group M1 and M2 were treated by injecting intraperitoneally with a dose of 20 mL/kg body weight 0.25% melatonin at 30 min before and after L-Arg induced.Rats were killed at the 6th,12th and 24th hour after the last time of L-Arg injection.The pathological changes of pancreatic and lung tissues were respectively analyzed and scored according to Kusser's and Lei weizhang's standard.Results With time going,the pathological injuries of the pancreas and lung in group A were significantly more severe than those in group C(P0.01).However,injuries in group M1 were significantly more mild than those in group A,especially within the 6th and 12th(P0.01 or 0.05).The degree of pathological injury in M2 was between the degree of group A and M1,and the changes in group M1 were more mild than those in group M2.At the 24th hour,the serum amylase in group A was significantly higher than that in group C(P0.01),but M1 group was lower than that in group A,the serum amylase in group M2 was significantly lower than that in group A(P0.05).Conclusion Lung injury is closely related to pancreatic tissue injury in ANP.Melatonin may reduce the lung and pancreatic injury in ANP.The protective effect of pancreatic and lung in group M1 was stronger than group M2.