atrial natriuretic peptide

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atrial natriuretic peptide (ANP; atrial natriuretic hormone) A peptide hormone, produced by certain cells in the wall of the atrium of the heart, that promotes the excretion of sodium ions in the urine (i.e. natriuresis). Secretion of ANP is triggered by increased stretch of the atrial wall, due to raised blood pressure or increased blood volume. It acts to inhibit sodium reabsorption in the kidneys and the secretion of aldosterone by the adrenal glands. Consequently, sodium losses to urine are increased, and water follows by osmosis, thereby decreasing blood volume and blood pressure.