Abstract: AimTo study the plasma angiotensin II (Ang II) levels and the expressions of angiotensin II₁ receptor (AT₁) in blood vessels and kidneys in diabetic and high fat diet rats, and the effects of enalapril on plasma Ang II levels and the expressions of AT₁ in blood vessels and kidneys in diabetic rats. MethodsThe plasma Ang II level was assayed with ¹²⁵I-Ang II radioimmunoassay, and the expression of AT₁ in blood vessel and kidney was analyzed with immunohistochemical technique. Results The plasma Ang II level was significantly higher in type 2 diabetic rats (241±49) pg·mL^-1 than that in the control (71±22) pg·mL^-1, high fat diet group (151±29) pg·mL^-1 (P<0.01), and enalapril-treated groups (136±25) pg·mL^-1 (P<0.05). The plasma Ang II levels in high fat diet and in enalapril-treated groups were also significantly higher than that in control group (P<0.01). With immunohistochemical technique, it was found that the expression of AT₁ in endothelial cells of blood vessels, vascular smooth muscle cells, and kidneys in diabetic group increased. The expression of AT₁ in endothelial cells of blood vessels, vascular smooth muscle cells, and kidney in enalapril-treated group was similar to that in control group. ConclusionThe plasma Ang II levels and the expression of AT₁ in type 2 diabetic and high fat diet rats increased. Enalapril was shown to decrease the plasma Ang II level and downregulate the expression of AT₁ in blood vessels and kidneys in type 2 diabetic rats.