Atrial natriuretic peptie (ANP), atrial natriuretic factor (ANF), or atriopeptin, is a polypeptide hormone secreted by atrial myocytes that is involved in the homeostatic control of body water, sodium, potassium and adiposity. It is released by atrial myocytes, muscle cells in the atria of the heart, in response to high blood pressure. ANP acts to reduce the water, sodium and adipose loads on the circulatory system, thereby reducing blood pressure.