CHANGES IN CARDIOVASCULAR MASS, LEFT-VENTRICULAR PUMPING ABILITY AND AORTIC DISTENSIBILITY AFTER CALCIUM-ANTAGONISTS IN WISTAR-KYOTO AND SPONTANEOUSLY HYPERTENSIVE RATS

Objectives: To determine the effects of different dihydropyridine calcium antagonists on cardiovascular mass and function in normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). Methods: The rats were treated daily for 3 weeks with nitrendipine (20 mg/kg), nifedipine (30 mg/kg), nisoldipine (6 mg/kg) or their vehicles. At the conclusion of that period left ventricular pumping ability and aortic distensibilty were determined, and the aortic, cardiac and left and right ventricular masses. Results: Each drug reduced arterial pressure in both rat strains; each decreased left ventricular mass in SHR but not in WKY rats. All three agents increased right ventricular mass in WKY rats; only nisoldipine did so in SHR. Each compound improved left ventricular pumping ability in WKY rats, maintaining function even when pressure was abruptly increased to preteatment levels. In contrast, although all three calcium antagonists improved cardiac performance in SHR at the pharmacologically reduced pressures, pumping ability was not maintained when pressure was increased to pretreatment levels in nisoldipine-treated SHR. All three agents improved aortic distensibility in both strains, but only in SHR was reduced aortic mass demonstrated. Conclusions: These data not only continue to demonstrate a functional/structural dissociation associated with antihypertensive therapy, but also suggest subtle functional and structural effects that differ even within the same class of calcium antagonists.