| Objectives:Diabetes Mellitus(DM) is a Coronary Heart Disease Equivalent.Besides left ventricular dysfunction,right ventricular dysfunction also exists in the diabetic. Pulmonary hypertension is the main reason of right ventricular dysfunction.Patients with DM have significantly higher prevalence of pulmonary hypertension, independent of coronary artery disease,hypertension,heart failure or smoking. Endothelin-1(ET-1),Calcitonin gene-related peptide(CGRP) and Substance P(SP) are the key factors in the pathogenesis of Pulmonary hypertension.To make T2DM model by short-term high fat diet feeding and small amouts streptozotocin(STZ) via the tail vein.By observing ultrastructure of lung tissue and pathological changes under light microscope,measuring lung vascular parameters and the expression of ET-1,CGRP and SP,we studied the possible mechanism of pulmonary hypertension and right ventricular dysfunction in DM.Methods:12 male Wistar rats were randomly divided into normal(N) group(n=6) and DM group(n=6).N group rats were fed with normal diet.After fed with high fat diet for 8 weeks,DM group rats were injected with 30mg STZ/Kg WB via the tail vein.N group rats were injected with buffer solution.After 72 hours,blood glucose was more than 16.65mmol/L.20 weeks later,the rats were sacrificed and the lung samples were obtained:(1)Put samples in the solution of 2.5%glutaric dialdehyde and 1%osmium tetroxide to fixate and observed with transmission electron micro-scope; (2)Fixated with 10%formalin:①Observed the morphological changes of the lung by light microscope.②After lastic fiber staining,measuring the ratio of the vascular wall thickness/vascular external diameter(WT%) and ratio of vascular wall area/total vaseular area(WA%) of the lung arteries,companied by respiratory bronchioles and alveolar ducts.③Studied the expression of ET-1,CGRP and SP by immunohistochemistry,then mearsured average optical density and the ratio of the positive area and the total area of field of view with Image Analysis System to evaluate the intensity of positive expression.Results:①STZ injection for 3 days later,the rats became polydipsia,polyphagia, polyuria,weight loss or no obvious weight gain.After 20 weeks,compared with N group,the body weight decreased in DM group(P＜0.01),while the fasting blood glucose increased(P＜0.01).②Ultrastructure:The typeⅡalveolar epithelial cells microvilli of DM rats decreaed and osmiophilic lamellar bodies were rare.The interstitium of lung was unclear.The basement membrane of air-blood barrier was clear but the endothelial cells was not.③light microscope:The alveolar structure of N group rats were normal.Compared with N group,DM group rats had smaller alveolar space,thicker alveolar septa and more alveolars.Compared with N group, the ratio of the total area of alveolar septa and the total area of field of view in DM group rats increased(P＜0.05).④Weigert lastic fiber staining:In DM group,the lung arteries walls were thickened and inflammatory cells infiltrated.Compared with N group,WT%and WA%of DM group increased(P＞0.05),but it had no statistical significance.⑤Immunohistochemistry:ET-1 was expressed in lung vascular endothelial cells,alveolar macrophages,bronchial and alveolar epithelial cells,airway and vascular smooth muscle cells,lung neuroendocrine cells of both N and DM group rats.CGRP was expressed in alveolar epithelial cells,bronchial neuroendocrirte cells and vascular smooth muscle cells of both N and DM group rats.SP was expressed in lung neuroendocrine cells,bronchial epithelial cells and vascular smooth muscle cells of both N and DM group rats.Compared with N group,the DM group average optical density of ET-1 increased(P＜0.05),the ratio of the positive area and total area of field also increased(P＜0.05),the DM group average optical density of SP increased (P＜0.05),the ratio of the positive area and total area of field also increased(P＜0.05), the DM group average optical density of CGRP increased(P＞0.05) and the ratio of the positive area and total area of field also increased(P＞0.05).Conclusion:①The model of diabetic rats could be made by short-term high fat diet then small amounts STZ via the tail vein.②The DM rats lung ultrastructure showed the alveolar epithelial cells injured.Light microscopy showed the alveolar septa thickened,the alveolars volume reduced and the number of alveolar increased, suggesting that lung tissue might have hypoxia.③WT%and WA%of the lung artery had an upward trend.So,the changes of lung vascular structure might be the pathological basis of pulmonary hypertension in DM.④The expression of ET-1, CGRP and SP had an upward trend,that might be associated with the diabetic pulmonary hypertension and the right ventricular dysfunction.
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