The Protective Effect Of Limb Ischemic Preconditioning On Acute Lung Injury Induced By LPS Of Rats

Objectives: In order to observe the protective effect of noninvasive limb ischemic preconditioning on acute lung injury induced by lipopolysaccharide (LPS) of rats, the changes of lung function, white blood cells(WBC) and lactate dehydrogenase (LDH) in bronchoalveolar lavage fluid (BALF), serum superoxide dismutase(SOD) and malondialdehyd(MDA) have been tested, and the content of pulmonary surfactant-associated protein-A(SP-A) and pathological change of pulmonary tissue were also compared with control following animal model.Methods: Fifteen female SD rats were divided randomly into Control Group, Acute lung injury Group (ALI Group),Acute lung injury and noninvasive limb ischemic preconditioning Group (ALI+N-LIP Group). Pentobarbital sodium was used to anesthetize by intraperitoneal injection. Both lower extremities in ALI+N-LIP Group were bind with tourniquet for 5 minutes every time. The tourniquet was released for 5 minutes. The preconditioning was repeated for 3 times. After it, ALI models were established by LPS in intraperitoneal injection in ALI Group and ALI+N-LIP Group .The normal saline (NS) in tales doses was injected in Control Group. One hour later, all rats were separately stimulated by methacholine (Mch) in four doses (0.39ng/mL,0.78ng/mL, 1.56ng/mL,3.12ng/mL)in order. The airway resistance (AR) and dynamic compliance (Cdyn) were recorded by Buxco. Blood samples and BALF were collected, the amounts of WBC in BALF were counted by cytometry and the level of LDH in BALE was also tested by automatic biochemistry analyzer. The level of seram MDA and SOD were examined by chromatometry. The lung tissues were acquired to observe the content of pulmonary surfactant-associated protein-A (SP-A) by immunohisto- chemistry and pathological changes by HE.Results: 1. Compared with Control Group, AR in ALI Group was significantly increased (P<0.01) and Cdyn was decreased (P<0.01) after stimulus by Mch. The increasing rate of AR and decreasing rate of Cdyn in ALI+N-LIP Group were less than in ALI Group.2. Compared with Control Group, the level of WBC and LDH in BALF for ALI Group and ALI+N-LIP Group were higher(P<0.01). Those in ALI+N-LIP Group were much lower than ALI Group (P<0.05).3. Compared with Control Group, in ALI Group, the total activity of SOD was weaker (P<0.01) and the level of MDA was higher (P<0.01). In ALI+N-LIP Group, the total activity of SOD was higher and the level of MDA was lower than ALI Group.4. The content of SP-A in ALI+N-LIP Group was strongest in three groups (P<0.01), while that in ALI Group was weakest (P<0.01).5. Acute lung injury in different extend could be observed both in ALI Group and ALI+N-LIP Group. The pathological phenomenons were capillary hemorrhage, alveolar septum widened, fusion of pulmonary alveoli and inflammatory cell infiltrate. But the degree of injury in ALI+N-LIP Group was less than ALI Group.Conclusion: noninvasive limb ischemic preconditioning has protective effect on acute lung injury induced by LPS in rats. Their possible mechanisms are related to by improving the secretion of SP-A and antioxidation.