ACE inhibitors or angiotensin-converting enzyme inhibitors, are a group of pharmaceuticals that are used primarily in treatment of hypertension and congestive heart failure.
ACE inhibitors are used primarily in the treatment of hypertension, though they are also sometimes used in patients with cardiac failure, renal disease or systemic sclerosis ACEIs can also be used to treat diabetic nephropathy and left ventricular hypertrophy.
Mechanism of action
Angiotensin-converting enzyme inhibitors reduce the activity of the renin-angiotensin-aldosterone system.
The renin-angiotensin-aldosterone system (RAAS)
One mechanism for maintaining the blood pressure is the release of a protein called renin from cells in the kidney (to be specific, the juxtaglomerular apparatus). This produces another protein called angiotensin, which signals the adrenal gland to produce a hormone called aldosterone. This system is activated in response to a fall in blood pressure (hypotension) as well as markers of problems with the salt-water balance of the body, such as decreased sodium concentration in a part of the kidney known as the distal tubule, decreased blood volume and stimulation of the kidney by the sympathetic nervous system. In such a situation, the kidneys release renin, which acts as an enzyme and cuts off all but the first 10 amino-acid residues of angiotensinogen (a protein made in the liver, and which circulates in the blood). These 10 residues are then known as angiotensin I. Angiotensin I is then converted to angiotensin II by angiotensin converting enzyme (ACE) which removes a further 2 residues and is found in the pulmonary circulation as well as in the endothelium of many blood vessels. The system in general aims to increase blood pressure by increasing the amount of salt and water the body retains, although angiotensin is also very good at causing the blood vessels to tighten (a potent vasoconstrictor).
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