Investigation of local ACE activity and structural alterations during development of L-NAME-induced hypertension

Tonic basal release of nitric oxide (NO) by vascular endothelial cells controls blood pressure (BP) in the basal state. In the present study, we showed how serum and local angiotensin converting enzyme (ACE) alters during development of hypertension in chronic nitric oxide synthase blockade, a non-renin-dependent model of hypertension. Four experiments were performed in which animals were given N(omega)-nitro-L-arginine methyl ester (L-NAME) (50 mg kg(-1)) for 2, 4, 8 and 12 weeks. The control group rats received tap water. The ACE activity in serum, aorta, heart, kidney and lung was analyzed by high performance liquid chromatography (HPLC) and the structural change in aorta was investigated by measurement of cross-sectional area (CSA). Significant elevation of systolic blood pressure developed in chronically NO-blocked rats compared to controls. These results indicated that ACE activity in aortae and heart was gradually increased during development of hypertension and was more pronounced at higher blood pressure. Furthermore, there was a positive correlation between aortic cross-sectional area and elevation of blood pressure. These observations highlight the importance of the local ACE particularly in organs regulating hypertension (aorta and heart) during development of L-NAME-induced hypertension.