Role of Cardiovascular Aldosterone in Hypertension

Aldosterone plays an important role in the pathogenesis of cardiovascular disease. We have reported that aldosterone is synthesized in cardiovascular tissues and local aldosterone synthesis plays important roles for hypertension and cardiac hypertrophy. High sodium intake develops and accelerates vascular injury and cardiac hypertrophy in SHRSP. Plasma aldosterone concentrations and PRA were decreased by high salt intake in SHRSP. Aldosterone production, the expression of CYP11B2 mRNA and angiotensin II receptor AT1R mRNA in blood vessels were significantly increased by high salt intake. These results suggest that high salt intake increases aldosterone production and expression of the AT1R mRNA in the vascular tissue in SHRSP, which may contribute to the development of malignant hypertension in saltloaded SHRSP. However, there are several reports of conflicting data. Mineralocorticoid receptor (MR) binding is tightly regulated by the enzyme 11ß-hydroxysteroid dehydrogenase type 2 (11ß-HSD2) which selectively metabolizes glucocorticoids to inactive metabolites, thus allowing for MR activation by aldosterone. We have reported that decreased 11ß-HSD2 in blood vessels in Dahl salt-sensitive (DS) rats, a model for salt-sensitive hypertension. Local aldosterone excess may play a significant role in the salt sensitivity and development of hypertension. High sodium intake decreased circulating rennin-angiotensin-aldosterone system and increased blood pressure and cardiac hypertrophy in DS rats, which were prevented by the treatment with a selective MR antagonist, eplerenone. Eplerenone also improved endothelial nitric oxide synthase (eNOS) activity and eNOS mRNA expression in blood vessels in DS rats. These results further suggest that not only circulating aldosterone but also local aldosterone is of critical importance in the pathophysiology of cardiovascular disorders.