The effect of enalapril on the cardiac remodelling in ovariectomized spontaneously hypertensive rats

Angiotensin-converting enzyme inhibitors reduce the blood pressure (BP) and inhibit the generation of the angiotensin II from the inactive angiotensin I. Ten 28-week-old spontaneously hypertensive rats (SHRs) had their ovaries bilaterally removed and five rats were left intact and studied for 7 additional weeks: intact group, ovariectomized group (ovx SHRs) and ovariectomized + enalapril group (ovx + en). BP was higher in ovx SHRs and lower in treated ovx SHRs. Left ventricular (LV) mass index was greater in untreated ovx SHRs and smaller in ovx + en group. The LV cardiomyocyte (cmy) mean cross-sectional area, measured by stereology, was greater in ovx SHRs and smaller in both intact and ovx + en SHRs. Ovx significantly decreased the density of intramyocardial blood vessels (ive), but administration of enalapril was able to restore the density of the ive to that seen in intact group. The worst ive:cmy ratio was found in untreated ovx SHRs, the intact group showed a 90% greater ratio, and the treated ovx group showed a 150% greater ratio than the untreated ovx group. In conclusion, ovariectomy, in SHRs, causes cardiac hypertrophy and an unfavourable myocardial remodelling. Of the spectrum of changes seen, the major effect of enalapril appears to be mediated via an increase in the density of ive.