Aldosterone Induces Angiotensin-Converting-Enzyme Gene Expression in Cultured Neonatal Rat Cardiocytes

Abstract

Background — The cardiac renin-angiotensin-aldosterone system is activated in failing hearts in proportion to the severity of the disease. We hypothesized that a positive feedback mechanism might exist within this system and contribute to the progression of the heart failure. Methods and Results — To test this hypothesis, we examined whether angiotensin II or aldosterone induces the expression of angiotensin-converting-enzyme (ACE) mRNA in cultured neonatal rat ventricular cardiocytes. Expression of ACE mRNA was detected and quantified using real-time reverse transcription-polymerase chain reaction. Exposure to angiotensin II (10 −5 mol/L) for 24 hours had no significant effect on the expression of ACE mRNA (0.7±0.5-fold versus control, P =NS), but similar treatment with aldosterone (10 −5 mol/L) induced a 23.3±7.9-fold increase ( P <0.01) in ACE mRNA expression. The effect of aldosterone was both time- (maximal effect, 24 hours) and dose-dependent (EC 50 , 4×10 −7 mol/L), and it was significantly ( P <0.01) inhibited by spironolactone, a specific mineralocorticoid receptor antagonist. Conclusions — Aldosterone upregulates ACE mRNA expression, which is blocked by spironolactone in neonatal rat cardiocytes. Thus, spironolactone may suppress the progression of heart failure by blocking the effects of aldosterone and angiotensin II.