Atrial Natriuretic Factor: Key Concepts, Functions & Exam Guide

Atrial natriuretic peptide (ANP) was the first member of the natriuretic peptide (NP) family to be found in heart tissue. Since then, BNP (B-type natriuretic peptide), CNP (C-type natriuretic peptide), urodilatin, and DNP (Dendroaspis natriuretic peptide ) have been found in the brain, kidney cells, and snake venom, among other places. Two guanylyl cyclase (GC) receptors, A- and B-type, and a third receptor, the “clearance” C receptor, mediate NPs' physiological activities.

But new research suggests that NPs may have physiological effects through the C receptor. When GC receptors are turned on, cGMP goes up, which causes other things to happen inside the cell. NPs were first linked to cardiovascular homeostasis, but their receptors are found in many different organs, which suggests that they have a much more comprehensive range of functions. NPs have antiproliferative, antifibrotic, anti-inflammatory, insulin-like, and bone growth-regulating effects. NPs are needed for ovarian follicles to grow and mature, and they also control different functions in several glands.

The Discovery of ANP

A hormone that controls the amount of blood in the heart was thought to exist long before it was found. Gauer and Henry did some of the first studies to show that regulating volume is an integral part of the cardiovascular system. The experiments of de Wardener et al. led to the search for a natriuretic hormone. They found that dogs with their renal arteries blocked had a strong natriuretic effect that couldn't be explained by a change in aldosterone levels or glomerular filtration rate, which stayed the same in these experiments.

With the development of electron microscopy, specific atrial granules thought to be secretory were found and studied. This gave the search for a natriuretic hormone a new direction. Atrial granularity has been shown to depend on the body's water and mineral balance and how well the adrenal glands work. These observations were confirmed by de Bold et al., who did some essential experiments and found that injecting rats with an extract of rat atrial tissue made them pee and poop quickly, but only for a short time. When ANP, a hormone produced by the heart, was found, it was seen as a big step forward in the search for natriuretic hormones.

Atrial Natriuretic Factor

Atrial natriuretic factor (ANF) is a peptide only found in the secretory granules of atrial muscle cells. Multiple peptides with similar structures have been found in atrial tissues. All of these peptides come from the same 152-amino-acid precursor. ANF makes experimental animals drink and pee a lot, and it also relaxes the vascular smooth muscle that has been contracted. The natriuretic effects of ANF are likely caused by the fact that it has a striking impact on the kidneys' blood flow (most often, it increases the glomerular filtration rate).

ANF can also stop renin from being released in living cells and prevent aldosterone from being made both on its own and when it is stimulated. It lowers arterial blood pressure, likely since it relaxes blood vessels. This effect is robust in renin-dependent (and potentially other vasoconstricting) models of hypertension.

Role of ANF in the Functioning of Kidney

Atrial natriuretic factor (ANF) is a polypeptide hormone with 28 amino acids released mainly by the heart's atria when the atria are stretched. ANF works on the kidney to increase sodium excretion and Glomerular filtration rate, stop renal blood vessels from narrowing, and stop renin from being made. ANF antagonises vasoconstriction and moves the fluid in the cardiovascular system.

ANF is a potent inhibitor of aldosterone synthesis in the adrenal glands, where it resides. ANF is a big part of the natriuretic response to short-term and long-term volume overload. The ability of ANF to move fluid from the vascular compartment to the interstitial compartment acts as a buffer, stopping the plasma volume from growing too much when the total amount of extracellular fluid increases. GFR modulation and salt excretion via natriuresis can also be mediated by ANF, which acts as a physiological GFR modulator.

The Effects of ANF on Blood Pressure

Atrial natriuretic factor (ANF) decreases blood pressure in intact animals and is a vasodilator. In-vitro, ANF relaxes angiotensin II-contracted arteries. Compared to other experimental hypertensive models, renin-dependent models of renovascular hypertension seem more sensitive to the blood pressure-lowering effect of ANF in vivo.

Therapeutic Perspectives of ANF

Atrial natriuretic factor lowers the blood pressure throughout the body and increases the amount of excreted sodium. As a result, ANF is a candidate for use as a medication in treating individuals who suffer from hypertension and congestive heart failure. On the other hand, ANF can only be given intravenously and has a half-life of only three to four minutes. At the moment, there are no substances that can be used to stimulate the secretion of ANF. On the other hand, it has been suggested that lowering the rate at which endogenous ANF is catabolised can lead to an increase in the amount of ANF found in plasma.

Important Questions

1) How ANF is used therapeutically?

Ans: The ANF lowers the blood pressure throughout the body as well as increases the amount of sodium that is excreted.

2) What are the effects of ANF on Blood pressure?

Ans: ANF decreases blood pressure. ANF is a vasodilator in intact animals. In-vitro, ANF relaxes angiotensin II-contracted arteries. Compared to other experimental hypertensive models, renin-dependent models of renovascular hypertension seem to be more sensitive to the blood pressure-lowering effect of ANF in vivo.

Key Features

• ANP was the first NP discovered in cardiac tissue.

• ANF is a peptide discovered in atrial muscle cell secretory granules.

• Atrial tissues contain similar-structured peptides.

• These peptides all have the same 152-amino-acid precursor.