Renin-angiotensin family

A. Renin-angiotensin family. The major function of renin-angiotensin system (RAS) in periphery is to maintain body-fluid homeostasis and regulate blood pressure. 

Natriuretic peptides are naturally occurring substances in the body that oppose the activity of the renin-angiotensin system. The natriuretic peptide family consists of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP). All three natriuretic peptides are synthesized from cleavage of a larger precursor polypeptide. In the ventricles and brain, the synthesis of BNP predominates ANP is synthesized by cardiac myocytes predominately in the atria and CNP is synthesized in the brain, blood vessels, and kidney. 

If the blood pressure is still not controlled, a second agent should be added, using the opposite pair to the first drug e.g. if the patient is on an ACE inhibitor add a Calcium channel blocker or thiazide Diuretic (A+C or A+D), since both vasodilatation or diuresis will stimulate the renin-angiotensin system and turns nonrenin-dependent hypertension into renin-dependent hypertension). The combination B+D is associated with increased risk of diabetes and should be avoided in at-risk patients (obesity, family history). The combinations A+B or C+D usually produce a less than additive effect on blood pressure, but should be tried in patients still uncontrolled on more standard combinations. 

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