Stereology of cardiac hypertrophy induced by NO blockade in rats treated with enalapril and verapamil

OBJECTIVE: To quantify the structural myocardial response when chronic NO blockade hypertension is treated with antihypertensive drugs. STUDY DESIGN: Four groups of 10 male Wistar rats each were separated as follows: control, L-arginine-methyl-ester (NAME), L-NAME + angiotensin-converting inhibitor (enalapril), L-NAME+calcium channel blocker (verapamil). All animals' blood pressure (BP) was measured weekly. After 40 days of experimentation the heart mass/body mass ratio (HBR) was determined, and the volume densities of the cardiac components were shown by stereology (Vv[c] for cardiomyocytes, Vv[i] for cardiac interstitium and the mean cross-sectional area of cardiomyocytes, a[c]). RESULTS: Significant differences by comparison with the control group were: BP increased 71% and HBR increased 24% in the L-NAME group, Vv[c] was 15% smaller in L-NAME animals, while an increase of 11% occurred in the enalapril group and 7% in the verapamil group. Vv[i] increased 20% in the L-NAME group; however, it decreased 13% in the enalapril group and 10% in the verapamil group. a[c] Was 30% greater in the L-NAME group, 13.5% in the enalapril group and 8.5% in the verapamil group. a[c] Was 12.5% smaller in the enalapril group and 16% smaller in the verapamil group when L-NAME rats were compared. CONCLUSION: Stereology revealed an equivalent effect of enalapril and verapamil in reducing BP, cardiomyocyte hypertrophy and interstitial fibrosis in rats with NO synthesis blockade after six weeks of treatment.