Angiotensin Receptor Regulates Cardiac Hypertrophy and Transforming Growth Factor-β1 Expression

The role of angiotensin II via the angiotensin type 1 or type 2 receptor in the development of cardiac hypertrophy was determined in adult male Sprague-Dawley rats subjected to coarctation of the abdominal aorta. Five groups of animals were studied: coarctation, coarctation plus DuP 753, coarctation plus PD 123319, sham plus DuP 753, or sham operation. Type 1 receptor blockade was accomplished with DuP 753 given in the drinking water and type 2 blockade with PD 123319 delivered by osmotic minipumps beginning with the day of surgery until 72 hours after aortic coarctation. Mean carotid blood pressures and the carotid-femoral artery blood pressure gradients were not different among coarctation, coarctation plus DuP 753, and coarctation plus PD 123319 animals. However, ratios of heart weight to body weight were higher in coarctation (4.95±0.8) or coarctation plus PD 123319 (4.52±0.5) than in sham animals (3.6±0.4; P<.005 and .05, respectively). In coarctation plus DuP 753-treated animals heart weight-body weight ratios were not different from sham or sham plus DuP 753 animals (3.9±0.4 versus 3.6±0.4 or 3.3±0.08, respectively). Type 1 receptor mRNA levels were significantly increased in the coarctation group, with the highest levels in the coarctation plus DuP 753 and sham plus DuP 753 groups. To determine whether growth factors were involved in the hypertrophic process, we measured transforming growth factor-β₁ mRNA levels. Northern analysis demonstrated a twofold increase in coarctation animals compared with sham or coarctation plus DuP 753-treated animals. Therefore, cardiac hypertrophy induced by abdominal coarctation of the aorta is mediated by the angiotensin type 1 receptor and results in upregulation of the cardiac angiotensin type 1 and transforming growth factor-β₁ genes.