Effect of angiotensin converting enzyme inhibition on pressure-induced left ventricular hypertrophy in rats

The influence of angiotensin converting enzyme inhibition on the development of left ventricular (LV) hypertrophy due to stenosis of the aortic arch was studied in female Sprague-Dawley rats. The aortic arch was banded to an outer diameter of 1.0 mm. After 14 days, LV and right ventricular functional parameters and transstenotic pressure gradient were measured in anesthetized rats. In addition, regional heart weights were determined, and myocytes of three different heart regions were isolated and subjected to morphometric analysis. To inhibit the angiotensin converting enzyme, ramipril was administered orally by gavage in a single daily dose of 1 mg/kg. Rats with aortic stenosis showed a marked increase in LV systolic pressure, mean prestenotic aortic pressure, and LV stroke work compared with sham-operated rats and demonstrated a systolic transstenotic pressure gradient of 82 mm Hg. This increase in LV hemodynamic load was paralleled by the development of LV hypertrophy as determined by a 37% increase in LV weight and by a 20% increase in cell volume of isolated LV myocytes. Concomitant ramipril treatment did not significantly affect LV functional parameters. The transstenotic pressure gradient was the same as in untreated rats with aortic stenosis. Likewise, the weight gain of the LV as well as the development of cellular hypertrophy of the LV were not influenced. Thus, in this model, angiotensin converting enzyme inhibition did not reduce the development of LV hypertrophy independent of the hemodynamic load.