Since I have suddenly found this sort of conversations very interesting I decided to research this specifc topic and though it might be of interest to relay the following :
Atrial natriuretic peptide (ANP), atrial natriuretic factor (ANF), atrial natriuretic hormone (ANH), or atriopeptin, is a protein (polypeptide) hormone secreted by heart muscle cells. Its involved in the homeostatic control of body water, sodium, potassium and fat (adiposity). It is released by muscle cells in the upper chambers (atria) of the heart (atrial myocytes), in response to high blood pressure. ANP acts to reduce the water, sodium and adipose loads on the circulatory system, thereby reducing blood pressure
ANP is a 28-amino acid peptide with a 17-amino acid ring in the middle of the molecule.ANP was discovered in 1981 by a team in Kingston, Canada led by Adolfo J. de Bold after they made the seminal observation that injection of atrial (but not ventricular) tissue extracts into rats caused copious natriuresis.
Production
ANP is produced, stored and released by cardiac myocytes of the atria of the heart. It is released in response to atrial stretch and a variety of other signals induced by hypervolemia, exercise or caloric restriction. The hormone is constitutively expressed in the ventricle in response to stress induced by increased afterload (eg. increased ventricular pressure from aortic stenosis) or injury (eg. myocardial infarction).
ANP is secreted in response to:
Atrial distention, stretching of the vessel walls
Sympathetic stimulation of β-adrenoceptors
Raised sodium concentration (hypernatremia)
Angiotensin-II
Endothelin, a potent vasoconstrictor
The atria become distended by high extracellular fluid and blood volume, and atrial fibrillation. Notably, ANP secretion increases in response to immersion of the body in water, which causes atrial stretch due to an altered distribution of intravascular fluid. ANP secretion in response to exercise has also been demonstrated in horses.
Receptors
Three cell surface receptors have so far been identified on which ANP act, and these are designated ANPA, ANPB and ANPC. The ANPA and ANPB receptors have guanylate cyclase activity & mediate the biological effects by producing cGMP.
The ANPC receptor functions mainly as a clearance receptor by binding & sequestering ANP from the circulation.
All natriuretic peptides are bound by the ANPC receptor. Atrial natriuretic peptide and brain natriuretic peptide act through the ANPA and C-type natriuretic peptide through the ANPB receptor
Physiological effects
ANP binds to a set of receptors. Receptor-agonist binding causes reduction in blood volume therefore reduction in cardiac output & systemic bp. Lipolysis is increased & renal sodium reabsorption is decreased. The overall effect of ANP on the body is to counter increases in blood pressure & volume caused by the renin-angiotensin system.
Renal
Dilates the afferent glomerular arteriole, constricts the efferent glomerular arteriole, and relaxes the mesangial cells. This increases pressure in the glomerular capillaries, thus increasing the glomerular filtration rate (GFR), resulting in greater excretion of sodium and water.
Decreases sodium reabsorption in the distal convoluted tubule and cortical collecting duct of the nephron.
Inhibits renin secretion, thereby inhibiting the renin-angiotensin system.
Reduces aldosterone secretion by the adrenal cortex.
Vascular
Relaxes vascular smooth muscle in arterioles and venules by.
Cardiac
Inhibits maladaptive cardiac hypertrophy.
Hope it was a bit of an interesting read . B)
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