Objective: To establish a diabetes mellitus model and observe the changes of the ERK1/ERK2 expression on the retina of diabetic rats which were treated by the angiotensin Ⅱ receptor Ⅰ antagonist Valsartan and reveal the therapeutical mechanism of suppressing the rennin-angitensin system on the diabetic retinopathy. Method: 60 rats were divided into normal, diabetes mellitus and treatment group randomly. The diabetic rats model was induced by the peritoneal injection of STZ, and then was treated with Valsart...