ANP - Atrial Natriuretic Peptide | Elisa - Clia - Antibody - Protein

Background:

ANP orAtrial Natriuretic Peptide is a hormone that is primarily produced and released by cells in the atria of the heart in response to stretching of the atrial walls. ANP plays a crucial role in regulating fluid balance, blood pressure, and electrolyte homeostasis. ANP promotes the excretion of sodium and water by the kidneys, hence its name "natriuretic." This leads to increased urine production (diuresis) and decreased blood volume. ANP causes blood vessels to dilate, which helps to lower blood pressure. This effect is partly due to its ability to relax smooth muscle cells in blood vessel walls. ANP also suppresses the release of renin from the kidneys, which in turn decreases the production of angiotensin II. This leads to reduced aldosterone secretion, further contributing to decreased sodium reabsorption and water retention. Inhibition of ADH (Antidiuretic Hormone): ANP also inhibits the release of ADH from the pituitary gland, which helps to further promote diuresis and prevent excessive water retention. ANP binds to specific receptors called Natriuretic Peptide Receptors (NPR), particularly the subtype NPR-A (or NPR1). These receptors are located on the membranes of target cells, such as kidney tubules and blood vessel walls.

Protein Structure:

• PreproANP: ANP is initially synthesized as a precursor molecule called preproANP, which contains 151 amino acids.
• ProANP: After cleavage of a signal peptide, it becomes proANP, consisting of 126 amino acids.
• Active ANP: The biologically active form of ANP is a 28-amino acid peptide derived from the C-terminal end of the proANP molecule.

Classification and Subtypes:

ANP belongs to the natriuretic peptide family, which includes:

• Brain Natriuretic Peptide (BNP): Produced in the ventricles and involved in similar regulatory processes as ANP.
• C-type Natriuretic Peptide (CNP): Primarily found in the brain and vascular endothelial cells, with distinct roles in vasodilation and growth regulation.

Function and Biological Significance:

• Diuresis and Natriuresis: ANP promotes the excretion of sodium (natriuresis) and water (diuresis) by the kidneys, reducing blood volume and pressure.
• Vasodilation: It causes relaxation of vascular smooth muscle, leading to vasodilation and decreased peripheral resistance.
• Inhibition of Renin-Angiotensin-Aldosterone System (RAAS): ANP inhibits the secretion of renin and aldosterone, thereby counteracting the effects of the RAAS, which typically increases blood pressure and fluid retention.
• Anti-hypertrophic Effects: ANP prevents hypertrophy of cardiac myocytes, contributing to its cardioprotective effects.

Interactions:

• Natriuretic Peptide Receptors (NPRs): ANP exerts its effects by binding to specific receptors, primarily NPR-A and NPR-B, which are guanylyl cyclase-linked receptors. This binding increases cyclic GMP (cGMP) levels, mediating the physiological effects of ANP.
• Other Hormones: ANP interacts with other hormonal systems, including inhibiting the actions of vasopressin and endothelin, both of which contribute to fluid retention and vasoconstriction.

Clinical Issues:

• Hypertension: ANP levels are often elevated in patients with hypertension as a compensatory mechanism to reduce blood pressure.
• Heart Failure: Elevated levels of ANP are found in heart failure, where it serves as a marker for disease severity and prognosis. ANP levels correlate with the extent of atrial stretch and fluid overload.
• Therapeutic Uses: Synthetic analogs of ANP or drugs that enhance its activity are being explored for treating conditions like acute heart failure and hypertension. Nesiritide, a recombinant form of BNP, has been used clinically for acute decompensated heart failure.

Summary:

Atrial Natriuretic Peptide (ANP) is a critical hormone involved in maintaining cardiovascular homeostasis by promoting diuresis, natriuresis, and vasodilation, and inhibiting the renin-angiotensin-aldosterone system. Synthesized by the atrial myocytes of the heart, ANP helps to regulate blood pressure and fluid balance. It interacts with natriuretic peptide receptors to mediate its effects, and its levels are significant in clinical conditions such as hypertension and heart failure. Understanding the role and mechanisms of ANP continues to be vital for developing therapeutic strategies for cardiovascular diseases.