Converting Enzyme Inhibitors in the Treatment of Hypertension and of Cardiac Failure
In man the enzyme renin exists both in blood and the kidney partly in an active, and partly in an inactive form [1, 2,]. Active renin reacts with a circulating substrate, angiotensinogen, cleaving that substrate between a leucine and a valine residue to form the inactive decapeptide angiotensin I. Within the circulation, angiotensin I is in turn split by (angiotensin) converting enzyme (ACE), two amino acid residues are removed, and the principal active component of the renin system, the octapeptide angiotensin II, is formed. Angiotensin II has a wide range of physiological and pathophysiological actions: It raises blood pressure both by an immediate vasoconstrictor and a slower action; it stimulates the sympathetic nervous system at various sites; it inhibits vagal tone; at rather higher than physiological doses it stimulates vasopressin secretion; it has a wide range of direct renal effects; it can promote thirst; and it is an important regulator of aldosterone secretion. All of these actions are evidently concerned with the maintenance of arterial pressure and of the circulation. Not surprisingly, therefore, efforts have been made over the years to develop therapeutic agents which interfere with the renin-angiotensin system at various points.
KeywordsRenal Artery Stenosis Renovascular Hypertension Renal Plasma Flow Urea Excretion Renin System
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