atrial natriuretic peptide

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A peptide hormone that is produced by the right atrium of the heart in response to elevated blood pressure and stimulates the excretion of sodium and water by the kidneys.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun biochemistry A strong vasodilatory, peptide hormone, secreted by the cardiac muscle cells.