Cardioprotective effects of an angiotensin-converting-enzyme inhibitor, imidapril, and Ca2+ channel antagonist, amlodipine, in spontaneously hypertensive rats at established stage of hypertension.

The present study was performed to compare cardioprotective effects of an angiotensin-converting-enzyme inhibitor, imidapril, and of a Ca2+ channel antagonist, amlodipine, against the cardiac hypertrophy in male spontaneously hypertensive rats (SHRs) at the established stage of hypertension. Fifteen-week-old SHRs were given imidapril (2 and 5 mg/kg/day) or amlodipine (10 mg/kg/day) by gavage for 8 weeks. Three hours after the 1st treatment, imidapril moderately reduced blood pressure without changing heart rate, while amlodipine caused a marked reduction in blood pressure accompanied by transient tachycardia. At the end of the treatments, ventricular weight in the imidapril-treated groups was markedly lower, but that in the amlodipine-treated group was only slightly lower than that in the vehicle-treated group. Myocardial collagen content in the imidapril-treated group tended to be decreased, and significant reduction was observed in the low-dose group. In another experiment, the isolated heart of the imidapril-treated animals demonstrated better cardiac compliance than that in the vehicle-treated animals. In contrast, amlodipine failed to improve cardiac function. The present results suggest that imidapril possesses advantageous effects to prevent cardiac hypertrophy and deteriorated cardiac function in SHRs of established stage of hypertension as compared with amlodipine.