胰岛素对链脲佐菌素诱导的糖尿病大鼠视网膜血管内皮生长因子表达的影响

Insulin has no effect on vascular endothelial growth factor expression in the retina of streptozotocin-induced diabetic rats

目的观察胰岛素对链脲佐菌素（STZ）诱导的糖尿病大鼠视网膜血管内皮生长因子（VEGF）表达的影响。方法60只雄性Sprague-Dawley（SD）大鼠随机分为柠檬酸钠缓冲液对照组（CIT-CON）和STZ诱导糖尿病组（STZDM），每组各30只。16周时，在CI-CON组中随机抽取24只大鼠分为柠檬酸钠缓冲液对照组（A组）和柠檬酸钠缓冲液加胰岛素作用组（B组），每组各12只，剩余6只作为阴性对照。同时，在STZ-DM组中也随机抽取24只大鼠分为STZ诱导糖尿病组（C组）和STZ诱导糖尿病组加胰岛素作用组（D组），每组也为12只，同样剩余6只作为阴性对照。胰岛素作用组皮下注射4IU胰岛素，24h后处死各组大鼠，3只取眼球、4％多聚甲醛固定，供制备病理切片；9只取视网膜神经上皮层，保存于液氮中。实时聚合酶链反应（Real-time PCR）检测视网膜VEGF mRNA表达，免疫组织化学、蛋白免疫印迹（Western Blot）检测VEGF蛋白表达。结果胰岛素作用于正常对照大鼠和STZ诱导的糖尿病大鼠后，正常大鼠VEGF mRNA 表达为7．71±0．25，蛋白表达为0．4925±0．0122，分别与胰岛素作用前比较，差异均有统计学意义（t=5．32，3．97；P〈0．05）；STZ诱导的糖尿病大鼠VEGF mRNA表达为9．05±0．28，蛋白表达为0．5152±0．0109，分别与胰岛素作用前比较，差异均无统计学意义（t=0．34，0．36；P〉0．05）。结论胰岛素作用于STZ诱导的糖尿病大鼠不能显著上调视网膜VEGF mRNA和蛋白水平。

Objective To investigate if insulin can affect the expression of vascular endothelial growth factor （VEGF） in the retina of streptozotocin-induced diabetic rats. Methods A total of 60 male Sprague Dawley rats were randomly divided into sodium citrate buffer control group （CIT -CON, n= 30） and STZ- induced diabetic group （STZ-DM, n=30）. At the 16th week, 24 rats from CIT CON group at random were randomly divided to group A （sodium citrate buffer control group, n= 12） and group B （sodium citrate buffer plus insulin group, n= 12）. The remaining 6 rats from as CIT-CON group served as negative control. At the same time, 24 rats from STZ DM group at random were randomly divided to group C （STZ-induced diabetic group, n=12） and group D （STZ-induced diabetic plus insulin group, n= 12）. The remaining 6 rats from STZ DM group also served as negative control. 4 IU of insulin was injected subcutaneously to rats of group B and D. Immunohistochemistry, Western blot and Real time polymerase chain reaction （RT- PCR） were used to measure the expression level of VEGF protein and mRNA respectively. RESULTS Insulin significantly increased the VEGF mRNA （7.71±0.25 vs 5.36±0.37, t test P〈0. 05） and protein expression （0.4925 ± 0.0122 vs 0.4272 ± 0.0110, t test P〈0. 05） in the retina of CIT CON rats. However, in retina of STZ-DM rats, insulin had no effect on VEGF mRNA （8.92±0.27 vs 9.05±0.28, t test, P〉0.05） and protein expression （0.5152±0.0109 vs0.5099±0.0100, t test P〉0.05）. Conclusions Insulin had no effect on VEGF expression in the retina of STZ- DM rats.