Question

Is atrial natriuretic peptide a vasoconstrictor?

Answer 1

The NPPA gene encodes atrial natriuretic peptide (ANP) or atrial natriuretic factor (ANF), a natriuretic peptide hormone produced from the cardiac atria. The natriuretic peptides (ANP, BNP, and CNP) are a structurally related family of hormone/paracrine factors. ANP's principal purpose is to reduce the volume of enlarged extracellular fluid (ECF) by boosting salt excretion in the kidneys.

Complete answer:
When injected into test animals, atrial natriuretic peptide (ANP) may be isolated from rat hearts and found to stimulate fluid excretion by the kidneys. The mechanism of action of ANP is currently unknown. ANP may limit salt reabsorption in the renal tubules, but it is also known to improve the rate of glomerular filtration in the kidney and relax smooth muscle preparations, including those made from the kidney's arteries.

We investigated the effects of semi-purified and synthesised ANP on blood vessels in the kidneys of anaesthetized rats to better understand its mechanism of action. ANP produces a vasodilation of the blood arteries that supply the glomeruli, as well as a decrease in the number of glomeruli and the arterioles that drain them are constricted. This backs up the theory that the natriuretic response is aided by higher filtration pressure.

In humans and experimental animals, intravenous atrial natriuretic peptide (ANP) causes splanchnic vasoconstriction, which is accompanied with drops in blood pressure and/or cardiac output.
The 28-amino-acid polypeptide hormone atrial natriuretic factor (ANF) is released primarily by the heart atria in response to atrial strain. ANF operates on the kidney to promote salt excretion and GFR, limit renin secretion, and counteract renal vasoconstriction.

Note:
ANP is produced and secreted by cardiac muscle cells in the walls of the heart's atria. Volume receptors in these cells respond to greater arterial wall stretching caused by increased arterial blood volume. Secondary effects of ANP's blood volume reduction include decreased extracellular fluid (ECF) volume, improved cardiac ejection fraction with enhanced organ perfusion, lower blood pressure, and higher serum potassium.