Atrial Natriuretic Factor (ANF)

Atrial natriuretic factor (ANF), also called atrial natriuretic peptide, is released by the muscle cells of the heart's atria when they are excessively stretched by a high volume of blood returning to the heart - making the heart itself a hormone-secreting organ that helps regulate its own workload. Once released, ANF travels to the kidneys, where it increases sodium excretion and increases blood flow to the glomerulus by dilating the afferent arteriole while constricting the efferent arteriole. It also suppresses the very system described in the section above: it decreases aldosterone release from the adrenal cortex and decreases renin release, thereby lowering angiotensin II levels. In effect, ANF acts as a built-in counterweight to the renin-angiotensin-aldosterone system and to …