EFFECTS OF SUBCHRONIC TREATMENT WITH TRANDOLAPRIL AND ENALAPRIL ON CARDIOVASCULAR MORPHOLOGIC ALTERATIONS IN THE AGED SPONTANEOUSLY HYPERTENSIVE RAT WITH HEART-FAILURE

The effects of a 3-month treatment period with the angiotensin-convert ing enzyme (ACE) inhibitors trandolapril (0.3 mg/kg/day, p.o.) and ena lapril (10 mg/kg/day, p.o.) on hemodynamics, cardiac hypertrophy, and vascular structures were examined in old spontaneously hypertensive ra ts (SHRs) (24 months at the end of treatment) presenting with congesti ve heart failure. During the course of treatment, the mortality rate w as lower in the two treated groups than in the control group. At the e nd of treatment, serum ACE activity was inhibited by 63 and 33% by tra ndolapril and enalapril, respectively, but the decrease in blood press ure they induced was not significant. The atrial natriuretic factor (A NF) plasma levels and cyclic GMP urine excretion were about 10-fold an d 3-fold higher, respectively, in old SHRs than in old Wistar rats. Th ese values were markedly decreased by both ACE inhibitors. The ventric ular hypertrophy was greatly decreased by both compounds (-24% by tran dolapril and -26% by enalapril). In the aorta, the media hypertrophy w as significantly decreased and nuclear density increased to a similar extent by both ACE inhibitors. In the mesenteric artery, trandolapril treatment induced a complete regression of the media hypertrophy and a marked decrease in extracellular matrix surface. In addition, the col lagen network appeared less dissociated in the treated animals. Simila rly the nuclear density was increased and the surface of cell nuclei w as decreased by trandolapril. Enalapril appeared much less potent on t hese parameters. These data demonstrate that treatment with trandolapr il of aged SHRs presenting with heart failure results in an increase i n survival of the animals and a marked regression of cardiac and vascu lar hypertrophy. In addition, a protective action at the level of vasc ular structure could also be demonstrated in resistance vessels.