atrial natriuretic peptide

Atrial natriuretic peptide (ANP) is the heart’s own hormone for shedding excess salt and water. When the heart’s upper chambers stretch from too much blood volume, they release ANP, which tells the kidneys to dump sodium and fluid — lowering the pressure and volume the heart must cope with.

ANP is made and stored by muscle cells in the heart’s atria and released when atrial walls are stretched by high blood volume. The word “natriuretic” means promoting sodium excretion in urine; water follows the sodium, so ANP reduces blood volume. It also relaxes blood vessels (lowering blood pressure) and directly opposes the renin-angiotensin-aldosterone system, blocking renin and aldosterone release. In effect, it is the body’s built-in counterweight to fluid overload.

Clinically, ANP and its cousin BNP are released in heart failure as the strained heart tries to compensate. This makes natriuretic peptide levels in the blood a useful marker for diagnosing and monitoring heart failure, and the pathway has been exploited by drugs that prevent natriuretic peptide breakdown.