BACKGROUND: The present study aimed to determine the changes of endothelin (ET), nitric oxide, and atrial natriuretic peptide (ANP) systems in the kidney and aorta in angiotensin (Ang) II-induced hypertension. METHODS: Male Sprague-Dawley rats were used. Ang II (100 ng.min-1.kg-1) was infused through entire time course. Fourteen days after beginning the regimen, aorta and kidney were taken. The protein expression of nitroc oxide synthase (NOS) was determined by semiquantitative immunoblotting. The mRNA expression of components of ET, NOS, ANP system was determined by real-time polymerase chain reaction. RESULTS: Hypertension was developed in the experimental group. mRNA expression of ET-1 in the aorta and kidney was increased. The protein expression of endothelial NOS (eNOS) was decreased in the aorta, while that of inducible NOS and neuronal NOS remained unaltered. mRNA expression of ANP, natriuretic peptide type (NPR)-A, and NPR-C was not changed in the aorta. CONCLUSIONS: Based on these results, it seems that in Ang II-induced hypertensive rats, increased expression of ET-1 in the aorta and kidney, and decreased eNOS expression in the aorta contribute to the pathogenesis of hypertension.