If the cardiovascular system is overloaded with fluid, the problem is alleviated by excreting salts through the nephrons of the kidneys. As electrolyte salts are excreted, water will follow, and vascular pressure should fall. This is the action of the BNP hormone. It is a diuretic.
Once released, BNP stimulates natriuresis and water loss. This action works against aldosterone, which conserves sodium and water. BNP causes loss of sodium and water through the kidneys to relieve the ventricular wall stretch. It also increases renal blood flow and glomerular filtration rate.
