Establishment Of A Rat Model Of Severe Acute Pancreatitis With Mods And Its Time-phase Change Of Intra-abdominal Pressure And Tnf-a

Background and objectiveSevere acute pancreatitis (SAP) is currently one of the most difficult illness of pancreatic diseases. Because of its rapid onset, life-threatening effects, rapid development, the mortality rate of SAP is up to 20%-40%, and it becomes research focus and emphasis of gastroenterology and surgical department. Despite the current treatment technology continues to improve, it is still difficult to cut down the high mortality and its rapid progress. Early cause of death of SAP is now believed to be the systemic inflammatory response syndrome (SIRS) which inducing multiple organ dysfunction syndrome (MODS).Inflammatory mediators, especially TNF-a is produced as an earliest inflammatory mediator in the pathogenesis of SAP–associated SIRS , and also play an important role in the MODS process. Therefore, some scholars proposed an " anti-inflammatory media therapeutic window " from the onset of SAP to MODS stage , using anti-inflammatory treatment by targeting inflammatory mediators can reduce the incidence of MODS .In recent years, as the clinical report about cases of SAP who were complicated with intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) continue to increase ,in which the increasing intra-abdominal pressure (IAP) will finally result in concurrent IAH and ACS that leading to multiple organ dysfunction. Thus IAP may be taken as the only risk factor for ACS. It is now recognizing that SAP can produce IAH which will lead to pathophysiological change in patients with SAP.According to the present reports the incidence of intra-abdominal hypertension pressure in patients with SAP is about 40%,and ACS about 10%. If SAP is associated with ACS, it's mortality is as high as 60% to 70%. IAH and SIRS are intertwined and promoted with each other ,which can accelerate the process of MODS. Early detection of IAH, and actively taketing medical therapy or surgical decompression therapy can reverse further development of ACS,which can reduce the mortality of SAP.Because MODS is the main cause death in early phase of SAP, the relationship between the SAP- related IAH and organ failure is so far unknown. And clinical cases of SAP patients complicated with IAH / ACS is very limited, it is of great need to prepare clinically relevant animal model, by pathophysiologically inducing SAP animal model related to MODS and IAH / ACS.Currently, many literatures reported an rat model of ANP induced by injection of sodium taurocholate into the pancreatic duc can lead to multiple organ damage; some scholars in 2007 first reported a rat model of ANP induced by 3.5% sodium taurocholate complicated with multiple organ pathology injury ,and the model may be taken as the ideal model for SAP complated with MODS, but the authors did not carry out research and compare multiple levels.An Ideal animal model of SAP with MODS not only should have a similarity to human's SAP in morphology, course and treatment response ,but also have a higher incidence of MODS and long survival time, so we first carry out multiple sodium taurocholate concentrations to induce ANP complicated MODS model to set up and seek a animal model with higher a incidence of MODS and long survival rate. Intra-abdominal pressure , TNF-a phase change in each model group and control group were also tested at the same time.We focused on the observation in the time-phase change of intra-abdominal pressure and TNF-a and its laws in ANP model which induced by the best concentration of sodium taurocholate.Therefore, our study is divided into the following two sections:(A) Preparation method of a rat model of severe acute pancreatitis with MODS: We first carryed out multiple sodium taurocholate concentrations to induce ANP animal model and seeked an animal model which had a higher MODS incidence and higher survival rate.The aim is to establish an ideal animal model of ANP complicated with MODS , which will be taken as an ideal animal model for drug intervention in SAP complicated with MODS(B) Study on time-phase change of intra-abdominal pressure and blood TNF-a in severe acute pancreatitis models:Based on the first part of the research, blood TNF-a, serum amylase, pancreas pathology score, were dynamically observed in 24h in order to explore the relationship between severity of pancreatitis ,intra-abdominal pressure and TNF-a and the experiment layed a foundation for further study of SAP complated with IAH/ACS.Method(A) Preparation method of a rat model of severe acute pancreatitis with MODS: 280 SD rats were randomly divided into control group(n=40) and 3.5%,4%,4.5%,5% ANP group(n=60 respectively). ANP groups were induced by retrograde injection of NaTc solution into the pancreatic duct of rats. 40 rats in each model group were sacrificed at 1,3,6,12 and 24h after the models were induced. Serum amylase, serum total bilirubin, Cr, blood gas analysis of rats,and pathological changes of pancreas were determined. Survival rate at 24 h was observed in another 20 ANP rats.(B) Study on the Time-phase change of intra-abdominal pressure (IAP) and TNF-a in rat model of severe acute pancreatitis: ANP group (n=40) was induced by retrograde injection of 4.5% sodium taurocholate into the pancreatic duct in SD rats while control group (n=40) was induced by saline at the same dosage. Eight rats in each group were killed at 1h,3h,6h,12h and 24h respectively. IAP, pancreatitis pathomorphologic score, the plasma levels of TNF-a and amylase were evaluatedResults(A) Preparation method of a rat model of severe acute pancreatitis with MODS:①In each model groups, the serum amylase level and the indicatrix of liver,renal and respiratory function showed significant dose-effect relationship and time-effect relationship with the change of concentration of NaTc as time passed.②Pancreatic pathology scores of ANP group at different time points were significantly higher than that of control group.③In 4.5% group, the dysfunction of liver and kidney were reached its peak at 6h,while the lung dysfunction was reached its peak at 12 h. The incidence of MODS was 52.5%, and 24 h survival rate of 4.5% group was 65% which was significantly higher than in 5%group.(B) Study on the time-phase change of intra-abdominal pressure (IAP), TNF-a in rat models with cute necrosis pancreatitis:①The levels of amylase in ANP group went up in progress with time which were significantly higher than that in control group at each time.②Incidence of IAP significantly rose compared with control group, and compared with the control group ,it was as three times as high as in 3h group and nine times higher in 12h group.③The levels of TNF-a were significantly higher than that in control group and reached its peak at 6h group.④The pathomorphologic score which began to deteriorate in 1h group and pancreatic necrosis occured in 3 h which reached its peak at 24h group.Conclusions1 The study of dose-effect relationship of Sodium taurocholate which induce ANP model with MODS showed that 4.5% NaTc solution may be an ideal concentration to establish the ANP model complicated with MODS.The incidence of MODS was 52.5% and survival rate in 24 hour was 65%.2 The study on time-effect relationship of best induced concentration showed that the level of TNF-a reached its peak at 6th hour . IAH was frequent in ANP rats injected with 4.5% NaTc solution, which may be the secondary response to inflammatory reaction..