Atrial natriuretic factor (ANF) is a powerful vasodilator, and a
protein hormone secreted by heart muscle cells. It is involved in
the homeostatic control of body water, sodium, potassium and fat
(adipose tissue). It is released by muscle cells in the upper
chambers (atria) of the heart (atrial myocytes) in response to high
blood volume. ANP acts to reduce the water, sodium and adipose
loads on the circulatory system, thereby reducing blood pressure.