Angiotensins

• Angiotensin-converting enzyme inhibitors (ACEIs) Pril’s
• Angiotensin II receptor blockers (ARBs) Sartans

RENNIN ANGIOTENSIN ALDESTERON SYSTEM RENIN:

It is a proteolytic enzyme secreted by the kidney into the blood stream. Stimuli that increase renin secretion: Sodium depletion, diuretics, hypotension, hemorrhage, upright posture, dehydration, constriction of renal artery, heart failure and Cirrhosis

• A1 (Can be converted by all tissues) ⇒ A2
• (Kinase, Cathepsin helps ACE to convert 1 to 2
• BradykineninRR lowers A2
• ACEE, ARBS

Actions of Angiotensins

• Angiotensin I (precursor of angiotensin II): It has no pharmacological action.
• Angiotensin II: It acts on two receptors; AT1 and AT2 receptors

Its action on AT1 receptor produces the following:

CVS:

• Arteriolar constriction leading to increased systolic and diastolic blood pressure (40 times as active as norepinephrine).
• Angiotensin II produces positive inotropic and chronotropic effects which are primarily due to central and peripheral sympathetic stimulation.   Endocrine:
• Increase secretion and synthesis of aldosterone which causes Na and water retention.
• Facilitate catecholamine synthesis and release.
• Increase pituitary vasopressin and ACTH.

Renal:

• Suppress renin release
• V.C of renal efferent arterioles, increases proximal tubular Na+ reabsorption

C.N.S

• Increase H2O intake and vasopressin secretion.
• Stimulate central sympathetic discharge.  

Its action on AT2 receptor produces the following:

• Antiproliferation.
• Apoptosis (normal cell death).
• Vasodilatation and increase local bradykinin.

Inhibitors of the renin-Ang system:

• Inhibitors of renin release: Beta-blockers carvidelol, labetalol, bucindolol, celiprolol, dilevalol α-methyldopa (Adrenergic Neuron Blocker) , clonidine (Central a2 stimulant)

• Inhibitors of plasma renin activity: aliskrine.

• Inhibitors of Ang-2 formation: angiotensin-converting enzyme inhibitors (ACEIs)(pril)

• Blockers of AT receptors: saralasin, losartan, valsartan