ANF is released by walls of atria or auricles. ANF (Atrial Natiuretic Factor) is secreted in response to increase of B.P. or blood volume.
ANF checks the secretion of renin-angitensin mechanism, and thus inhibits reabsorption of NaCl by collecting duct and also stops release of aldosterone. ANF is a vasodilator whereas the Angiotensin II is a vasocontrictor.