Abstract: Objective To observe the gene expression of atrial natriuretic peptide （ANP） in ventricles and plasma and the effect of enalapril treatment in diabetic rats by streptozicin 60 mg/kg I.P.Methods Plasma ANP concentrations were determined in Wistar rats with RIA at 1, 3, 5 month after establishment of experimental diabets model. Semi-quantitative RT-PCR was used to evaluate the left ventricular ANP mRNA content, and heart weight index（HWI） were recorded. A group of diabetic rats were treated with enalapril（2 mg/kg·d） for 5 months.Results The plasma ANP levels in diabetic rats were increased at 1-month （1528.5±354.2 vs 1134.1±368.3）pg/mL（P=0.064） and at 3-month （1747.8±346.2 vs 1220.1±355.1）pg/mL（P＜0.05） as compared to control. At 5-month, however, the plasma concentrations of ANP were not different between diabetics and control（1047.9±317.4 vs 914.1±205.0）pg/mL（P=NS）. The left ventricular ANP mRNA contents in diabetic rats were increased at 1-month （1.559±0.501 vs 1.041±0.404）pg/mL（P=0.051） and then were reversed to normal level at 5-month （1.317±0.362 vs 1.177±0.472）pg/mL（P=NS）. In enalapril-treated diabetic rats, the plasma ANP concentrations were significantly higher than that in diabetic rats（1405.9±360.7 vs 1047.9±317.4）（pg/mL）（P＜0.05） and control （1405.9±360.7 vs 914.1±205.0）pg/mL（P＜0.05）, while the gene expression were not augmented. Conclusion Enhanced ventricular gene expression and elevated plasma levels of ANP was found at the early stage of diabetes.Enalapril treatment increased the plasma ANP concentrationsin diabetic rats, which is perhaps one of mechanisms underlying the effect of enalapril on heart function improvement and myocardium preservation.