- A-type natriuretic peptides are also called atrial natriuretic peptides. They're made, stored and released largely by the atria, muscle cells in the upper chambers of the heart. The body makes more A-type natriuretic peptide in response to high blood pressure and stretching of the atria. These conditions are often seen in congestive heart failure, where increased blood volume and higher levels of extracellular fluid (fluid overload) stretch the heart's walls. In patients with heart failure, A-type natriuretic peptides are also made by the ventricles, cells in the heart's lower chambers -- the pumping chambers.
A-type natriuretic peptide causes a reduction in blood volume and therefore a reduction in heart output and blood pressure. Excretion of sodium by the kidneys and the breakdown of fat cells are also increased.
- B-type natriuretic peptides are also called brain natriuretic peptides. B-type natriuretic peptides are made, stored and released mainly by the ventricles. It's produced in response to stretching of the ventricles due to the increased blood volume and higher levels of extracellular fluid (fluid overload) that accompany congestive heart failure. It acts as a natural diuretic, eliminating fluid, relaxing blood vessels and funneling sodium into the urine.
When your heart is damaged, your body secretes very high levels of B-type natriuretic peptide into your bloodstream in an effort to ease the strain on your heart. The levels may also rise if you have new or increasing chest pain (unstable angina) or after a heart attack.
- C-type natriuretic peptides are produced by cells that line the blood vessels. They cause relaxation of blood vessels, helping to lower blood pressure. Unlike A-type and B-type natriuretic peptides, they don't have direct natriuretic activity.