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 aldosterone is small compared with that of the adrenal, raising the question of its function in normal conditions. Moreover, the regulation of this synthesis in pathophysiologic states remains unknown. In an analysis of the effects of a one-month myocardial infarction (MI) on the cardiac steroidogenic system, it was observed that aldosterone-synthase mRNA and the aldosterone concentration were increased by 2- and 3.5-fold, respectively, in the noninfarcted part of the rat left ventricle. MI also induced a 1. 9-fold increase in the cardiac angiotensin II level. Losartan prevented these changes, and the MI-induced collagen deposition in noninfarcted area of the left ventricle was reduced by 1.6- and 2. 5-fold by both spironolactone and losartan treatments, respectively. Thus, these observations indicate that MI is associated with tissue-specific activation of myocardial aldosterone synthesis. This activation is mediated by cardiac angiotensin II via the angiotensin II type 1 (AT1) receptor, and the resultant increase of intracardiac aldosterone level may be involved in post-MI ventricular remodeling.