The Influence Of Leptin On The Expression Of NO And NOS In Rats With Acute Pancreatitis

ObjectiveIn the pathogenesy of AP, the theory of cytokine and inflammatory reaction has been generally accepted by everyone .Some inflammatory transmitter which mediatly causing by cytokine in AP ,can make neutrophilic leukocyte sticking and gathering in region. The cytokine and inflammatory transmitter produced by activated neutrophilic leukocyte can bring out cytotoxic effect to regional part,the changes of vasopermeability,the aggregation of blood plate, these changes can make pancreatic microcirculation disturbance,aggravating injury of pancreas.The infernal circle will induce the pancreas and peripancreatic tissue autodigestion,the cytokine produced by regional inflammatory reaction enter the blood circulation, keep on producing large cytokines ,lead to systemic effect,so the regional inflammatory reaction advancing to SIRS.Leptin is a 16 kDa protein encoded by the obese (ob) gene. Leptin is produced and secreted by various cell, especially adipocytes. plasma leptin level corresponds very closely to the amount of fat tissue Leptin reaches the hypothalamus via a blood to induce satiety by suppression of neuropeptide Y release . Reducing the food intake, leptin plays a crucial role in the homeostasis of body weight and energy expenditure.Nitric oxide(NO) is a potent vasorelaxant factor formed when L-arginine(L-Arg) is converted to L-citrulline by the function of NO synthase (NOS), and plays a major role in the microcirculatory changes. It has been exist the controversy about its function in the AP. Some studies found that NO have a protective function to the pancreas organization in the AP,which acts indirectly via increasing pancreatic microvascular blood flow (PMBF). But other studies think, NO is useless or harmful, associated with oxidant stress and vasodilatation and hypotension causing local hemodynamic disturbances. So NO was regarded as a regulatory anti-inflammatory cytokines and also as a proinflammatory, cytotoxic cytokines.To date three isoforms of NOS have been identified: neuronal constitutive (nNOS or NOS-1), inducible NOS (iNOS or NOS-2)and endothelial constitutive (eNOS or NOS-3). See from the function of NOS, the NOS was divided into two kinds of forms: constitutive NO synthase (cNOS) and inducible NO synthase (iNOS) .The cNOS exists in brain and endothelial cell, which are constantly present and synthesize small amounts of NO in response to physical or receptor stimulation. Its physiological actions are mainly mediated by cyclic guanosine monophosphate (cGMP), cousing vasodilatation. The iNOS exist in macrophage ,vascular smooth muscle cell,activated neutrophil and endothelial cell,the iNOS is a kind of pathologic enzyme. The iNOS is found only after stimuli such as endotoxin or proinflammatory cytokines,and generates large amounts of NO in a sustained. Excess production of NO causes vasodilatation and local hemodynamic disturbances. Recent years, the research thinks that an increasing formation of NO by iNOS plays an important role in the development of acute pancreatitis, and inhibition of NO production has a beneficial effect on reducing pancreatic inflammation。leptin stimulates a nitric oxide (NO) release from different tissues such as: fat tissue vascular endothelium pituitary gland and also pancreatic acinar cells. But the effet of NO is controversy,some studies found that inhibition of NO synthaseaggravates the pancreatic damage in the course of acute pancreatitis.So if Leptin functions through NOS in the actue pancreatitis, and thefunction the increased NO stimulated by Leptin is protective or deleterious. Through this experiment we can observe the certain relationship between Leptin and NO , NOS.The experiment explore the effect of Leptin on the expression of NOS and NO in rats with acute pancreatitis (AP) and to investigate leptin in the treatment of AP.Methods1.Measurement the contents of NO₂^-/NO₃^- in the pancreas tissueThe NO₂^-/NO₃^- kit provided by Nanjing Jiancheng Bioengineering Institute. carry on the operation and calculation under the instruction2. Measurement the activity of NOS in the pancreas tissueThe NOS kit provided by Sigma company.Making use of the isotope marking method measure activity of iNOS and cNOS .3.Histological examination.Results1.Compared with the sham operation group, the contents of NO and iNOS and pathological grade in the pancreas tissue is obvious higher in the AP group,but the activity of cNOS is obviously lower.2.Compared with the AP group, the activity of cNOS increased, while the contents of NO and the activity of iNOS decreased obviously,and its pathological grade is obviously lower than the AP group.ConclusionIn summary,the results of this experiment, in the actue pancreatitis, the activity of cNOS is obviously lower excess production of NO by iNOS has a cytotoxic effect.Leptin could reduce this effect and extenuate pancreatic damage in the course of acute pancreatitis. The protective and healing effects of leptin appears to be dependent on increasing the activity of cNOS and decreasing the activity of iNOS. These data taken together with a result suggests that the Leptin is an important protective factor in the acute pancreatitis. This experiment provides the solid theories foundation for the further clinical application.