Spironolactone Improves Angiotensin-Induced Vascular Changes and Oxidative Stress

Abstract

Angiotensin II plays an important role in vascular remodeling. We investigated the role of aldosterone, which is stimulated by angiotensin II, as a mediator of angiotensin II–induced vascular structural and functional alterations. Sprague-Dawley rats (n=8 to 12/group) received angiotensin II (120 ng/kg per minute, subcutaneously) for 14 days ± spironolactone or hydralazine (25 mg/kg per day). An additional group received aldosterone (750 ng/h, subcutaneously) ± spironolactone. Systolic blood pressure was increased by angiotensin II ( P <0.001) and reduced by spironolactone and hydralazine ( P <0.001). Aldosterone-induced increase of blood pressure was reduced by spironolactone ( P <0.05). In mesenteric small arteries studied on a pressurized myograph, media/lumen ratio was increased ( P <0.001) and acetylcholine-mediated relaxation was impaired in angiotensin II–infused rats ( P <0.001); both were partially improved by spironolactone ( P <0.05) but not by hydralazine. Aldosterone-induced increase of media/lumen ratio ( P <0.001) and impaired response to acetylcholine ( P <0.001) were normalized by spironolactone. Response to sodium nitroprusside was similar in all groups. Aortic NADPH oxidase activity was increased ( P <0.01) by angiotensin II and reduced by spironolactone and hydralazine. Aldosterone also increased ( P <0.05) activation of NADPH oxidase, an effect abolished by spironolactone. Plasma thiobarbituric acid–reactive substances (a marker of oxidative stress), higher in angiotensin II and aldosterone rats ( P <0.001), were normalized by spironolactone. In conclusion, spironolactone, which inhibited aldosterone actions, partially corrected structural and functional angiotensin II–induced abnormalities. These effects were associated with reduced vascular NADPH oxidase activity and decreased plasma markers of oxidative stress. Our findings suggest that aldosterone may mediate some of angiotensin II–induced vascular effects in hypertension, in part via increased oxidative stress.