LEFT-VENTRICULAR HYPERTROPHY IN THE SPONTANEOUSLY HYPERTENSIVE RAT - EFFECT OF ACE-INHIBITORS ON ULTRASTRUCTURAL MORPHOLOGY

The ACE inhibitors cilazapril and captopril were administered at 10 an d 100 mg/day, respectively, to spontaneously hypertensive (SHR) and no rmotensive Wistar-Kyoto rats (WKY) from the 12th to the 22nd week of l ife. Both drugs produced statistically significant reductions in systo lic and diastolic blood pressure, left-ventricular mass and index of l eft-ventricular hypertrophy in SHR. After cilazapril treatment, the mo rphology of SHR cardiocytes became similar to that in untreated normot ensive rats, while in captopril-treated rats, myofibrils were disarran ged, obliquely oriented and smaller than normal, with areas of electro n-transparent sarcoplasm separating the myofibril bundles; mitochondri a were also altered. In WKY rats, we observed no statistically signifi cant changes in blood pressure, ventricular weight and hypertrophy ind ex between the two drugs; however, there were different effects of the two drugs on the ultrastructural morphology of the myocardium. These observations suggest that these two molecularly dissimilar ACE inhibit ors act differently at the tissue level despite similar effects on blo od pressure and left-ventricular mass.