Effect of melatonin, captopril, spironolactone and simvastatin on blood pressure and left ventricular remodelling in spontaneously hypertensive rats.

Objective: Melatonin was shown to reduce blood pressure, oxidative load and to increase nitric oxide bioavailability predisposing melatonin to have antiremodelling potential.

Design: The aim of this study was to show whether melatonin can reverse left ventricular remodelling in spontaneously hypertensive rats (SHR) and to compare this potential protective effect with captopril, spironolactone, or simvastatin.

Methods: Six groups of 3-month old rats (eight per group) were treated for 5 weeks: control untreated Wistar rats, control SHR, SHR plus melatonin (10 mg/kg per 24 h), SHR plus captopril (100 mg/kg per 24 h), SHR plus spironolactone (200 mg/kg per 24 h) and SHR plus simvastatin (10 mg/kg per 24 h). Their systolic blood pressure (SBP) was measured by the tail-cuff method. The relative weights of the left ventricle, nitric oxide synthase (NOS) activity, endothelial NOS and nuclear factor kappa B (NF-kappaB) protein expression, conjugated dienes concentration, level of collagenous proteins and hydroxyproline were measured.

Results: SBP was reduced by all drugs investigated but most prominently by captopril in SHR. The activity of NOS and endothelial NOS expression increased in the left ventricles of SHR compared with controls. Melatonin and spironolactone further increased NOS expression. Left ventricular oxidative load, estimated by NF-kappaB expression and conjugated dienes concentration, increased in SHR. Only melatonin reduced NF-kappaB expression and decreased conjugated diens concentration. Only captopril reduced left ventricular hypertrophy in SHR, whereas melatonin reduced collagenous protein concentration and hydroxyproline content in the left ventricle.

Conclusion: It is concluded that although melatonin, in comparison with captopril, did not reverse left ventricle hypertrophy, it reversed left ventricular fibrosis. This protection by melatonin may be caused by its prominent antioxidative effect.