Question

List the hormones secreted by atrium?

Answer 1

Hint: Atrium is the upper chamber of the heart where the blood flows through. In the human heart there are two atria. For cardiovascular and renal homeostatic processes, the right atrium releases the hormone.

Complete answer:
Atrial natriuretic peptide (ANP) or atrial natriuretic factor (ANF) is a natural peptide hormone secreted by the cardiac atria (hormone formed by the heart's right atrium) encoded by the NPPA gene in humans. Natriuretic peptides (ANP, BNP, and CNP) form a family of structurally related hormone / paracrine factors. Such natriuretic factors are of particular importance both physiologically and clinically, as they are involved in controlling cardiovascular and homeostatic renal processes. They are interested in controlling the volume and electrolyte balance of body fluids.

ANP 's key function is to minimise the amount of expanded extracellular fluid (ECF) by increasing sodium excretion in the renal system. ANP is synthesised in the walls of the atria in the heart and secreted by cardiac muscle cells. These cells contain volume receptors that lead to increased atrial wall stretching due to increased volume of blood in the atrium.

Significant decrease of blood volume by ANP can cause side effects such as decrease of extracellular fluid (ECF) volume, enhanced cardiac ejection fraction with resulting better organ perfusion, decreased blood pressure, and increased serum potassium. Different counter-regulatory pathways operating simultaneously on each of these side effects can blunt or negate these effects.

Additional information:
In 1981, when rat atrial extracts were found to contain a substance that increased the salt and urine production in the kidney, de Bold first announced the discovery of a natriuretic factor (one that promotes kidney excretion of salt and water). Subsequently, some groups isolated the substance from heart tissue and named atrial natriuretic factor (ANF) or ANP. ANP is synthesised as an inactive preprohormone, formed by the human gene NPPA situated mostly on chromosome short arm 1. In response, ANP is secreted to:
- Atrial wall stretching, via Atrial Volume Receptors.
- Increased Sympathetic β-adrenoceptor activation.
- While sodium concentration is not the main cause of increased secretion of ANP but increased concentration of sodium induces hypernatremia.
- Efficient vasoconstrictor called Endothelin.

Note: Beliefs on using ANP for treating acute heart failure and kidney disease are different. Newly synthesised ANP molecule homologues for the treatment of acute heart failure are being tested. Preliminary research on one of these molecules, ularitide, has shown that in the treatment of acute heart failure this medication is safe, well tolerated, and successful.