| OBJECTIVES: 1.To establish an appropriate model of focal cerebral ischemia-reperfusion in experimental chronic diabetic rats and normal rats, then comparatively analyze the factors influencing successful preparation of the model .2.To observe the expressiones of VEGF and CD31 in focal cerebral ischemia reperfusion model in experimental chronic diabetic rats and normal rats, then analyzed the reasons why the expressionses of VEGF and CD31 were different at the same trauma of cerebral ischemia-reperfusion in experimental chronic diabetic rats and normal rats, and analyzed the relationships between diabetes and cerebrovascular angiosis.METHODS: 1.The establish of the model about experimental chronic diabetic rat: a total of 140 male Wister rats weighing 180 to 220g were injected intraperitoneally a bolus dosage of streptozotocin (STZ) 55mg/kg after fasting 12 h, feeding with ordinary food for 42~47d and adding gentamycin(6.4×10~4U/rat) twice in drinking water every 7d .Then chronic experimental diabetic rats weighing 240 to 310g and blood glucose 13.5 to 25.6mmol/L were selected to establish the cerebral ischemia reperfusion model.2.The establish of the model about cerebral ischemia-reperfusion: Ninety chronic experimental diabetic rats and ninety non-diabetic male Wister rats were selected to establish cerebral ischemia-reperfusion model by Longa'technique respectively. Therats were randomly assigned to normal control group, sham, receiving reperfusion lh, 3h, 6h, 12h, 24h, 72h, 168h by weight and blood glucose randomly with every group has 10 rats. The successful establishing rate of both groups of rat model was compared and the causes of fail and death in rat model establishing were analyzed by evaluation with Longa neurofunction scale.One day after reperfusion for various periods, rats were anesthetized and brains were then removed and the specimens were cut into 6 slices from the frontal pole with 2 um thickness. The forth were put into 10% formaldehyde then embedded in paraffin ,by using immunohistochemistry we investigated the expression of VEGF and CD31 in ischemic core and penumbra in different periods of reperfusion from 1 hour to 168 hours , in normal control group and sham in diabetic rats and non-diabetic rats.RESULTS: 1.The establishment of diabetic model:The standard of chronic diabetic rat model was blood glucose level > 13.5mmol/L.Only 90 rats were successful established diabetic model in 140 rats.The blood glucose level increased and body mass decreased in diabetic group rats during experiment.lt demonstrated there was significant difference compared with those controls. Intolerance of STZ(n=19,13.57 %)and restoring the function of pancreas islets with normal blood glucose level (n=31,22.14 %) were the main cause in chronic diabetic group.2.The establishment of cerebral ischemia reperfusion model:The neurofunction scale in non-diabetic cerebral ischemia reperfusion rats was lower than those in diabetic cerebral ischemia reperfusion group. The gross specimen and histopathological change in both successfully established rat model were similar on the whole except the shifting time of brain median line structure in group of diabetic rat was shorter than that in the group of non-diabetic rat , and the area of cerebral edema in diabetic rat was larger than that in non-diabetic rat.The first important cause for failure was intracerebral hemorrhage(n=5,41.67%) in non-diabetic cerebral ischemia reperfusion group;and the cerebral edema(n=14,48.28%) was the main cause in chronic diabetic cerebral ischemia reperfusion group.3. The expression of VEGF : The expression of VEGF was negative in normal contral of diabetic or non-diabetic rat and in sham of non-diabetic.The expression of VEGF was slightly positive in sham of diabetic rat .After reperfusion, diabetic rat:It was found that the expression of VEGF started at lh,and subsequently increased,reached peak value at 3h in ischemic core then decrease, failed away until 7d,while reaching peak value at 12h in penumbra then decrease.Non-diabetic rat:it was at 3h that the expression of VEGF reached peak value in ischemic core then decrease and at 24h that reached peak value in penumbra then decrease.At every point of reperfusion,the expression of VEGF in diabetic rat is smaller than non-diaetic rat in ischemic core or penumbra (P<0.05). 4. The expression of CD31: The expression of CD31 was negative at lh of reperfusion in endotheliocyte in both diabetic and non-diabetic rat.The expression of CD31 increase gradually at 72h in capillaries, and reached peak value in 168h in both rats.At every point of reperfusion after 24h, the expression of CD31 in non-diabetic rat was larger than that in diabetic rat (P<0.05).CONCLUSION: l.We chose body mass of 180~220g male Wister rat to establish the modle of focal cerebral ischemia reperfusion model in experimental chronic diabetic rat.At the 35 day of breeding,we measured blood glucose and weight of diabetic rat and choose those blood glucose between 13.5— 26.5mmol/L with weight between 220g~300g successful to the model of chronic experimental diabetic rat,then we chose those diabetic rats to establish the model of cerebral ischemic reperfusion. 2. The trauma of ischemic stroke of diabetes rat was serious than that of non-diabetes rat.We can see,the less of the function of nerve was larger, the grade point was higher ( P<0.05 K infarction volum was larger in diabetic rat.3.The expression of VEGF in diabetic rat was smaller than non-diabetic rat in ischemic core or penumbra at every point ofreperfusion (P<0.05).That prompted that the deficiency of VEGF indiabetic rat may take part in the pathological and recovery process of ischemic stroke.4.The expression of CD31 was smaller in capillaries in diabetic rat than innon-diabetic rat at every point after reperfusion 24h (P<0.05).That is to say thedensity of vascular is lower in diabetic rat,and the angiogenesis was poor in diabetic rat.
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