Expression Of Aquaporin-1 In The Rats' Myocardium And Its Relationship With Myocardial Edema In Early Stage Postburn

BackgroundsSince shock is a hemocircular dysfunction and heart is a motivational organ in the circulation system, the cardiac function crucially influences the occurrence and development of shock. After a series of studies, it is found by the Third Military University researchers that myocardial damage and functional impairment of myocardium occurs immediately following severe burns even before significant reduction in blood volume secondary to increase of capillary permeability, and such prompt myocardial damage leads to cardiac deficiency, and it is also a precipitating factor for burn shock and ischemic/hypoxic injury of systemic tissues and organs, so called shock heart hypothesis. Serious burns can result in "shock heart", which causes cardiac damage, not only changes in myocardial function, but also myocardial organic changes. However that the early postburn myocardial injury mechanism is rather complex, mainly four aspects:1. Myocardial ischemia and reperfusion injury; 2. Myocardial tissue edema; 3. Cardiomyocytes of oxygen utilization and energy metabolism disorders; 4. Uncontrolled inflammatory response. According to study found significant myocardial edema in three hours after burn, and often left behind after burn shock stage of myocardial edema and myocardial cells to destroy the lives of normal activities; To oxygen diffusion to the cells from prolonged reduction of myocardial oxygen consumption, mitochondrial damage, energy metabolism; myocardial tissue congestion or ischemia, exacerbates the damage,with the extension of ischemic time, myocardial fiber fracture, microvascular injury, myocardial no-reflow phenomenon occurs. It is more complex mechanisms of myocardial edema after burn.Recent studies have found that hypoxic ischemic injury and myocardial edema and necrosis close.Because myocardial cell edema limits myocardial blood flow and myocardial nutrient supply, which contributed to the injury after myocardial ischemia. It can be considered, myocardial edema is an important part of myocardial ischemia-reperfusion injury, and further promotes myocardial ischemia-reperfusion injury after hypoxia occurrence and development.There are two basic ways in transmembrane transport of water:through the cell membrane lipid bilayer by simple diffusion and mediated water transport, which is the main form of water transport through membrane, water channel protein-mediated transport of water important conditions. Domestic and international studies have found that, AQP in the brain edema, pulmonary edema formation, the development of diabetes insipidus, tumor prognosis has played an important role in.Aquaporin protein is about to increasing the water permeability of cell membranes and to promoting the osmotic pressure driven water transport across cells. Where AQP-1 is subject to the most extensive and in-depth study of a water channel subtype, is also the first to be confirmed under the effect of osmotic pressure driven water transport across the cell membrane of the Aquaporin proteins. In mammals, Aquaporin-1 are widely distributed among a variety of tissues and organs, including the red blood cells, blood vessels, kidneys, lungs, brain, eye and heart, and involved in the pathophysiology of a variety of functional regulation. Further research found that in these tissues, which AQP-1 expression significantly in non-fenestrated capillaries and venules of the endothelial cells. In addition, some non-vascular tissue of the endothelial cells (such as eye cornea, sclera and intestinal lacteal) also exist AQP-1 expression. AQP-1 is based on the basic physiological functions, suggesting endothelial cells in the vascular tissue expression of Aquaproin-1 protein may be possibly involved in the inter-endothelial osmotic water transport. Studies have confirmed that, AQP-1 exists in myocardial tissue is the most important of water channel protein subtype, which it is mainly expressed in the myocardium of the microvascular endothelial cells and cardiac cells. The results suggest that many of myocardial edema in the process of AQP-1 play an important role. Such as right through the blood dilution due to the long-term low-permeability state of embryonic heart in animal studies found that myocardial edema accompanied by the AQP-1 gene transcription and protein expression levels increased, and acute myocardial ischemia-reperfusion injury study also found increased AQP-1 expression resulted in myocardial edema.However, myocardial tissue resulting from hypoxic-ischemic injury leading to myocardial edema after burn expression of AQP-1 in myocardium have not yet been reported at domestic and external.In this study, the establishment of a 30%TBSAⅢdegree burn model, the application of the method of immunohistochemical and ELISA observation of postburn myocardial ischemia AQP-1 expression and its relationship with the dynamic changes of the correlation between myocardial edema. And the combination of AQP-1 inhibitors acetazolamide application, aimed at understanding to altere expressions of AQP-1 in burned rats'myocardium, followed by postburn to explore myocardial edema and water transport function of AQP-1 protein in the inner potential contact. To further clarify the postburn "shock heart" to provide a theoretical basis for the mechanism.Objectives1. Observed burns in animal models of AQP-1 in cardiac tissue distribution and expression dynamics after burn.2. Explore AQP-1 water transmembrane transport protein function and myocardial edema after burn.Methods1. Animal model:90 healthy adult Wistar rats (from the Experimental Animal Center of Southern Medical University), weights (210±20) g, In accordance with random number table were randomly divided into three groups:normal control group A (n= 6), a simple burn group B (n= 42), burn plus acetazolamide group C (n= 42). Where B, C group after injury, each for 2 h,4 h,8 h,12 h,24 h,48 h and 72 h total of seven observation time points, each time point for 6 rats. One day before sealded, hair on rats'back was depilated by 100g/L sodium sulfide.30g/L sodium amytal was injected into the abdominal cavity for anesthesia with the dosage of (40mg/kg) before sealded, then 30% TBSA deep third degree scald was made by immersing rats in 100℃hot water for 15 s. After injury, according to Parkland formula perkilogram of body weight for every 1%of the burn area 4ml intraperitoneal injection of compound sodium lactate Ringer's solution would be half of the total is divided into two equal portions, immediately after injury and injected 3 h after injury, the other half is divided into four and so on copies after injury 8 h,12 h,16 h, and 24 h into the injured after two 24-hour, the liquid volume by half, divided into 3 sub-uniform rehydration. C group also intraperitoneally injected fluid burns 5%acetazolamide (100mg/kg·d), was completely injected 30 minutes after injury.2. Test index and Methods:Respectively, the depth of anesthesia at different time points rats were killed, take left ventricular myocardial tissue pathology to do light microscope observation; Immunohistochemical method to detect myocardial tissue at different time points and expression of AQP-1 distribution characteristics; Using ELISA determination at each time point of myocardial tissue homogenate supernatant AQP-1 content; Use wet and dry weight method to determine water content in myocardial tissue.3. Statistical analysis:All the data presented by X±s, and analyzed by statistieal software of SPSS 13.0. This experiment is 3×7* 6 factorial design, line completely randomized two factor factorial analysis (two-way analysis of variance), to understand the various variables of the main effects and interaction; method of multiple comparisons between Group using Bonferroni and SNK, use correlation and linear regression analysis between AQP-1 and water content in myocardial tissue. P< 0.05 presents statistics different.Results1. Pathological and morphologic change:Hematoxylin-eosin staining (HE) show a clear structure A group of myocardial, endocardial endothelial integrity, and interstitial connective tissue type was no inflammatory cell infiltration, no edema and connective tissue hyperplasia, cardiac cells, a clear cross striations, nuclear center epicardium endothelial integrity, and non-exudate lining and inflammatory cell infiltration. Group B after injury 2 h, myocardial injury lesions began to appear; injury 8 h, marked swelling of myocardial cells, myofilament disarray, some muscle fibers wavy; After injury 12 h, further aggravated the disease, cells ill-defined, interstitial vascular dilatation and congestion, some heart cells can be found in vacuolar degeneration of myocardial cells, edema, cell body increases, endocardial endothelium is not complete, a large number of myocardial degeneration and necrosis, There are a large number of interstitial lymphocytes, macrophages, diffuse infiltration.2. AQP-1 widely distributed in the myocardium, and is mainly distributed in the myocardial microvascular and myocardial cell membrane. Group B after severe burn AQP-1 in myocardial tissue showed increased expression of the trend. AQP-1 in the B group of myocardial tissue after burn 2 h (9.920±0.40 ng/ml) which was significantly higher (P<0.01); 12 h (19.14±1.01 ng/ml) and reached the peak and sustained at a high level,48 h 13.65±0.45 ng/ml expression level was still higher than normal. However, AQP-1 in the C group of myocardial tissue after injury 4 h (10.50±0.49ng/ml),12 h (13.60±0.97 ng/ml),48 h (8.73±0.41 ng/ml) myocardial tissue expression of AQP-1 significantly reduced compared with the B group (P< 0.01).3. Postbum myocardial water content was significantly higher than the normal control group (73.29±0.04%), myocardial water content began to increase after burn 2 h, and reached the peak after 12 h(80.79±0.12%), then decreased gradually after burn 48 h (76.93±0.1%) in still higher than normal levels (P<0.01). While at the same time point in each C group 8 h (75.49±1.09%),12 h (76.49±1.1%),48 h (74.59±1.04%) the degree of myocardial edema compared with group B significantly reduced (P<0.01). Acetazolamide intervention can inhibit the extent of myocardial edema. Within a certain time, the degree of myocardial edema and AQP-1 related protein expression.4. Myocardial tissue after burn AQP-1 expression in myocardial tissue water content changes and correlation analysis(r= 0.844 P<0.01), between the two shows a significant positive correlation.Conclusions1. The existence of myocardial tissue of rats AQP-1 protein expression, there are mainly in the microvascular endothelial cells and myocardial cells on the sarcolemma.2. AQP-1 expression was significantly increased after burn. To AQP-1 inhibitor acetazolamide can obviously reduce the burn myocardial tissue AQP-1 expression.3. Myocardial tissue in rats after burns and myocardial edema AQP-1 increased expression was positively correlated, AQP-1 inhibitor acetazolamide expression by inhibiting AQP-1 to reduce myocardial edema. Therefore AQP-1 play an important role in the development process, which in rat myocardial edema after burn.