ANF(Atrial natriuretic factor) is a protein hormone which is secreted by the atrial wall in response to the high blood volume and high blood pressure into the circulatory blood. ANP maintains the homeostasis of electrolytes by binding to an ANP Receptor -Antagonist. Binding causes the increase in renal sodium excretion, which results in a decreased ECF and blood volume. Hence Atrial natriuretic factor is released by Heart.So, the correct answer is 'Heart'.