Cardiovascular hypertrophy: role of angiotensin II and bradykinin

Angiotensin II can raise blood pressure rapidly by inducing direct vasoconstriction and by activating the sympathetic nervous system via central and peripheral mechanisms. In addition, this peptide may act as a growth factor to cause vascular and cardiac hypertrophy (CVH). The structural changes caused by hypertension can therefore be amplified by angiotensin II. Blockade of angiotensin II generation with angiotensin-converting enzyme (ACE) inhibitors appears to be particularly effective in preventing the development of cardiovascular hypertrophy. This beneficial effect might be related to some extent to local accumulation of bradykinin. ACE is one of the enzymes physiologically involved in bradykinin degradation. Treatment of hypertensive rats with a selective bradykinin antagonist can attenuate the blood pressure-lowering effect of ACE inhibition and render less effective the prevention of intimal thickening after endothelial removal from the rat carotid artery. Bradykinin is a vasodilator that acts by increasing the release of endothelium-derived factors such as nitric oxide and prostacyclin, which may have antiproliferative activity. However, blockade of the renin-angiotensin system with an angiotensin II subtype 1-receptor antagonist is also effective in preventing cardiac hypertrophy and neointimal proliferation after endothelial injury. Therefore, the exact contribution of bradykinin to the beneficial effects of ACE inhibition on cardiovascular hypertrophy remains to be further explored.