Dissociation of changes in cardiovascular mass and performance with angiotensin-converting enzyme inhibitors in Wistar-Kyoto and spontaneously hypertensive rats. The effects of angiotensin-converting enzyme inhibitors on cardiovascular mass and function were measured in three groups of 22 week old male Wistar-Kyoto normotensive and spontaneously hypertensive rats treated with CGS-16617, cilazapril or quinapril. Left ventricular performance was assessed by electromagnetic flow meter during rapid whole blood infusion before and after arterial pressure and increased abruptly with aortic snare; aortic distensibility also was assessed in vitro. The systemic hemodynamic effects of these three agents were similar, yet their structural effects varied. Although left ventricular and aortic masses diminished and right ventricular mass remained unchanged (with all three agents) in the spontaneously hypertensive rats, CGS-11617 and cilazapril also reduced left ventricular mass in the normotensive Wistar-Kyoto rats without changing aortic mass. All three agents improved aortic distensibility whether or not mass was decreased. Left ventricular structural changes were associated with variable changes in pumping ability. These data show that reduced mass associated with angiotensin-converting enzyme inhibitor treatment was not consistent in ventricles and aorta, that a dissociation exists between structural and functional changes and that reduction of cardiac mass alone does not relate to changes in chamber mass or in function. Thus, biologic and pharmacodynamic differences exist among angiotensin-converting enzyme inhibitors as well as between classes of antihypertensive agents. 