| Objective:At present, obesity is an epidemic disease in the world. It is the risk factor of cardiovascular disease, hypertensive disease, diabetes and other diseases. Obesity predispose people to hypertension. And the heart as the the vital organs in the cardiovascular system is associated with the occurrence and development of hypertension. The heart is not only a dynamic organ, but also an endocrine organ which has the function of the secretion of atrial natriuretic peptide (atrial natriureticpolypeptide, ANP); Moreover, the quantity of the atrial natriuretic peptide granules (ANP granules) are very large in right atrium and the largest in right auricle. ANP has the functions of natriuresis, diuresis and vasorelaxant, it also has a major affect on the regulation of blood pressure, so that its concentration relates with the process of hypertension. But it is not very clear for the relation between ANP and obesity, and lack of morphological evidence. In this study, we observed the right auricle tissue in obesity rats by light microscopy and electron microscopy, and compared the reactions of ANP between obesity rats and normal rats by immunohistochemical technology to reveal the subtle and ultrastructural characteristics of the right auricle of obesity rat, investigate the different ANP reactions between obesity rats and normal rats, provide the morphological evidence for the form and characteristic of secreting ANP.Methods:1Grouping of the animal and preparation of modelChose ten healthy adult male SD rats, and divided all the rats into two groups randomly:control group and high-fat diet group. The rats in normal group were given feed normally, and the rats in high-fat diet group were given high fat diet for ten weeks. Then executed all of animals and cut their right auricles.2Light microscopy sample preparation and observationThe right auricle tissues of hight-fat diet group and control group in paraffin-embedded was stained by hematoxylin-eosin(HE) and observed by the light microscope (light microscope, LM). Observed the structure of the right auricle, the array of three membranes, The distribution of blood vessels and Lymphatic, the differences between control group and high-fat diet group.3Immunohistochemical staining and light microscope observationThe right auricle tissues of control and high-fat diet group in paraffin-embedded was stained by immunohistochemical staining of ANP. And selected some tissues to stained by PBS as the control group. Observed the distribution of ANP in right auricle tissue, and contrasted the differences between control and high-fat diet group.4TEM sample preparation and observationPrepared the ultra-thin right auricle tissue sample, and observed by transmission electron microscope (TEM). Observed the ultrastructural characteristics of right auricle and the distribution of atrial granules; observed the Structural characteristic of blood capillary and lymphatic capillary among the atrial cells.5SEM sample preparation and observationPrepared the right auricle tissue into the conventional sample, and observed the surfaces of endocardium and epicardium by scanning electron microscopy (scanning electron microscope, SEM).Results:1LM observation of HE staining:The right auricle is composed by three structure:endocardium, myocardium and epicardium. The connective tissue and a layer of epithelial cells form the epicardium. In different parts, the connective tissues have different thickness. We can see many blood and lymphatic vessels in here. The myocardium is under the epicardium. There are the ring and the longitudinal arrangement of myocardial fiber. These fibers connect each other as a net, and there are many capillaries in the mesh. The innermost part is endocardium. It is composed of the flat endothelial cells and endocardial connective tissue.In the control group, the shape, edge and size of atrial cell nucleus are normal. The myocardial fibers arrange regularly, and the interstitial structure is normal too; however, from the right auricle of high-fat diet group,we can see some differences. The nucleus become crude. Their edges become rough. The myocardial fibers are disordered. The interstitial substances are broaden.2LM observation of immunohistochemical staining:In the group of PBS, the immune responses of ANP appear negative results. However, in the control group of ANP, the immune responses appear positive results widely. The result means that ANP exist in right auricle. ANP appear as brown colored granules. They distributed aroud the nucleus. Among the fibers, there are a few granules.In the high-fat diet group, the immune responses of ANP are stronger than control group, and brown colored granules increased significantly.3TEM observation:The pinacocyte cells compose the epicardial epithelium and endocardial endothelium. The connections between epithelial cells are fluffy. There are a lot of finger tubby protrusions. We call them microvillus. These microvilluses extend to the surface of pericardial cavity and basis; the connections between endothelial cells are closely, and their microvilluses are smaller. We can see loose connective tissues under epithelium and endothelium. The major composition of connective tissue is collagen fiber. We also can find the blood and lymphatic vessels, nerves, etc.On the longitudinal section surface of atrial cells, there are a lot of sarcomeres and mitochondrias. Golgi complexes and lots of secretory granules are around the nucleus; the shape of granule are round or oval; They have a high electron concentration. They are homogeneous, and rapped with membranes; there are many granules near the cell membrane. These granules which were wrapped by cell membrane and cytoplasm form papillary protrusions. In the gap of atrial cell, we can see some granules which were discharged. We can see blood and lymphatic capillary among the cells. The lymphatic capillary has thinner wall and bigger cavity. Its shape is not normal. We can observe granular substances and rags in the cavity. But the endothelium of blood capillary is thicker. We can see red blood cell in its cavity.In the high-fat diet group, the cells appear lipidosis or steatosis, and it becomes hypertrophy. The edge of nucleus becomes rough. The gap between atrial cells becomes bigger. The secretory granules in cell increase generally.4SEM observation:The epicardial epithelium of rat is pinacocyte cell. The cell has rough shape and wavy edge. Its center bulges slightly. There are many microvilluses on the surface of epithelium. The microvilluses at junction of adjacent cells are longer and more. We can see epithelial stomata structure in here.The endocardium of right auricle is smoother and neater. The endothelium has cord-like and fold-like arrangements. The microvilluses of endothelium are short and sparsity. On the surface of endocardium, we can see muscle bundles appeared carination uplift which were called pectinate muscles.Conclusion:1Feeding the rat with high-fat diet can lead it to obesity and increase its weight. Nutritive obesity model can be successfully established.2Obesity rats happen the structural changes of myocardium tissues. The changes lead fat to deposition, bring about steatosis of cardiac muscle fiber and even cause hypertrophy of myocardial cell.3The immune responses of ANP of Obesity rats in right auricle enhance obviously, and the places of response have an appreciable increase. Obesity will cause the increase of secreting ANP for compensatory adjustment of blood pressure; it prompt that obesity is associated with the occurrence and development of heart disease. |
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