ANP; a 28 amino acid peptide (alpha-ANP), derived from cardiac atria, several smaller fragments of alpha-ANP, and adimer of alpha-ANP with 56 amino acids (beta-ANP) that are present in plasma in heart failure. ANP actions includeincreasing capillary filtration, and renal salt and water excretion, and decreasing arterial pressure and the secretion ofrenin, angiotensin, aldosterone, and antidiuretic hormone. Syn: atriopeptin, cardionatrin.