What is Atrial Natriuretic Factor (ANF)?

Atrial Natriuretic Factor, also known as Atrial Natriuretic Peptide (ANP), is a peptide hormone primarily secreted by the cardiac atria in response to atrial wall stretch, which occurs during increased blood volume and pressure.

It plays a critical role in maintaining cardiovascular homeostasis by:

• Promoting natriuresis (excretion of sodium) in the kidneys.

• Inducing vasodilation to reduce blood pressure.

• Inhibiting the renin-angiotensin-aldosterone system (RAAS) to decrease fluid retention.

• Regulating extracellular fluid volume.

Evidence and Classification

• Multiple studies and authoritative resources classify ANF as a hormone because it is secreted into the bloodstream and acts on distant organs, such as the kidneys and blood vessels.wikipedia+3

• ANF belongs to the natriuretic peptide family with similar peptides like brain natriuretic peptide (BNP).

• It binds to specific receptors (e.g., NPRA) which mediate its biological effects through cyclic GMP signaling.

Why ANF is Not a Neurotransmitter, Enzyme, or Growth Factor

• Neurotransmitter: ANF is not released at synapses or involved in neuronal signaling.

• Enzyme: ANF is not a catalytic protein but a signaling peptide.

• Growth Factor: ANF does not primarily stimulate cell growth or differentiation.

Summary Table

Conclusion

The correct classification of atrial natriuretic factor secreted from the cardiac atria is:

(1) Hormone