Cardiac aldosterone production and ventricular remodeling

An intracardiac production of aldosterone has been recently reported in rat . This production is increased both acutely and chronically by angiotensin II. observations suggesting that the heart contains a steroidogenic system that is regulated similarly to the adrenal one. Cardiac production of aldos terone is small compared with that of the adrenal. raising the question of its Function in normal conditions. Moreover. the regulation of this synthes is in pathophysiologic states remains unknown. In an analysis of the effect s of a one-month myocardial infarction (MI) on the cardiac steroidogenic sy stem. it was observed that aldosterone-synthase mRNA and the aldosterone co ncentration were increased by 2- and 3.5-fold. respectively, in the noninfa rcted part of the rat left ventricle. MI also induced a 1.9-fold increase i n the cardiac angiotensin II level. Losartan prevented these changes, and t he MI induced collagen deposition in noninfarcted area of the left ventricl e was reduced by 1.6- and 2.5-fold by both spironolactone and losartan trea tments, respectively. Thus, these observations indicate that MI is associat ed with tissue-specific activation of myocardial aldosterone synthesis. Thi s activation is mediated by cardiac angiotensin II via the angiotensin II t ype 1 (AT1) receptor, and the resultant increase of intracardiac aldosteron e level may be involved in post-MI ventricular remodeling.