The name of 2 related proteins involved in regulating blood pressure. The 1st, angiotensin I, is inactive and is formed when renin, which is produced by the kidneys, acts on the substance angiotensinogen. Angiotensin I is then converted to the second, active, form, angiotensin , by angiotensin-converting enzyme. Angiotensin causes narrowing of the small blood vessels in tissues, resulting in increased blood pressure. It also stimulates release (from the adrenal cortex, the outer part of each adrenal gland) of the hormone aldosterone, which also increases blood pressure.
Certain kidney disorders can increase the production of angiotensin , causing hypertension. Whatever the cause of hypertension, it may be treated with drugs called ACE inhibitors, which work by reducing angiotensin formation.
A substance formed in tissues or blood vessels when there needs to be local or even massive vasoconstriction. The primary precursor is renin, made by the kidneys, and elevated when the blood seems dehydrated or low in volume; the next substance needed for this reaction is a liver protein, angiotensinogen; when both are present in the blood, local factors can then form this pressor substance. Excess production is often implicated in high blood pressure.
Angiotensin is a peptide that occurs in two forms: I and II. The former results from the action of the ENZYME, RENIN on alpha globulin (a protein) produced by the liver and passed into the blood. During passage of the blood through the lungs, angiotensin I is converted into an active form, angiotensin II, by an enzyme. This active form constricts the blood vessels and stimulates the release of two hormones – VASOPRESSIN and ALDOSTERONE – which raise the blood pressure. (See also
ANGIOTENSIN-CONVERTING ENZYME (ACE) INHIBITORS.)
n. either of two peptides: angiotensin I or angiotensin II. Angiotensin I is derived, by the action of the enzyme *renin, from a protein (alpha globulin) secreted by the liver into the bloodstream. As blood passes through the lungs, another enzyme, angiotensin-converting enzyme (ACE), acts on angiotensin I to form angiotensin II. This peptide causes constriction of blood vessels and stimulates the release of the hormones *vasopressin and *aldosterone, which increase blood pressure. See also ACE inhibitor; angiotensin II antagonist.
The ENZYME that converts angiotensin I to angiotensin II (see ANGIOTENSIN) is called angiotensin-converting enzyme. Angiotensin II controls the blood pressure and is the most potent endogenous pressor substance produced in the body; angiotensin I has no such pressor activity. Inhibition of the enzyme that converts angiotensin I to angiotensin II will thus have marked effects on lowering the blood pressure, and ACE inhibitors have a valuable role in treating heart failure when thiazides and beta blockers cannot be used or fail to work, especially after myocardial infarction (see HEART, DISEASES OF). Captopril was the ?rst ACE inhibitor to be synthesised: it reduces peripheral resistance by causing arteriolar dilatation and thus lowers blood pressure. Other drugs such as enalapril, lisinopril, cilazapril, quinapril and ramipril have since been developed. Some kidney disorders increase the production of angiotensin II and so cause HYPERTENSION.... angiotensin-convertingenzyme (ace) inhibitors
any one of a class of drugs that block the action of the hormone *angiotensin II, which constricts blood vessels; they are therefore useful in treating *hypertension. These drugs include candesartan, irbesartan, losartan, telmisartan, and valsartan. Side-effects are usually mild.... angiotensin ii antagonist
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