What is the Difference Between Angiotensin 1 and Angiotensin 2

The main difference between angiotensin 1 and angiotensin 2 is that angiotensin I is relatively inactive and has a lower affinity for angiotensin receptors than angiotensin II.

Angiotensin I is an inactive precursor that undergoes enzymatic conversion to angiotensin II, the biologically active hormone of the renin-angiotensin system. On the other hand, angiotensin II plays a central role in regulating blood pressure, fluid balance, and various physiological processes in the body.

Key Areas Covered

1. What is Angiotensin 1  
     – Definition, Structure, Features
2. What is Angiotensin 2
     – Definition, Structure, Features
3. Similarities Between Angiotensin 1 and Angiotensin 2
     – Outline of Common Features
4. Difference Between Angiotensin 1 and Angiotensin 2
     – Comparison of Key Differences

Key Terms

Angiotensin 1, Angiotensin 2

What is Angiotensin 1

Angiotensin I is an important component of the renin-angiotensin-aldosterone system (RAAS) and serves as the precursor to angiotensin II, a potent hormone involved in cardiovascular regulation. Angiotensin I is synthesized through the enzymatic cleavage of angiotensinogen, a liver-derived protein.

The production of angiotensin I begins with the release of renin, an enzyme primarily secreted by the juxtaglomerular cells of the kidney. Renin acts on angiotensinogen, which the liver constantly releases into the bloodstream. Renin cleaves angiotensinogen, resulting in the formation of angiotensin I, a decapeptide. Angiotensin I is a biologically inactive molecule and requires further enzymatic processing for its conversion to angiotensin II.

What is Angiotensin 2

Angiotensin II is a potent hormone and a crucial component of the renin-angiotensin-aldosterone system (RAAS). It is a peptide hormone that plays a significant role in regulating blood pressure, fluid balance, and cardiovascular homeostasis. Angiotensin II is generated through a complex enzymatic cascade involving the conversion of angiotensinogen to angiotensin I by renin, followed by the action of angiotensin-converting enzyme (ACE) to produce the active form, angiotensin II.

Angiotensin II synthesis primarily occurs in the kidneys. Renin cleaves angiotensinogen to form angiotensin I. Subsequently, ACE, primarily present in the lung endothelium, converts angiotensin I to angiotensin II by removing two amino acids. Angiotensin II acts on two main receptor subtypes: angiotensin type 1 (AT1) and angiotensin type 2 (AT2) receptors. AT1 receptors are widely distributed in various tissues, including vascular smooth muscle cells, adrenal cortex, heart, and brain, mediating angiotensin II’s vasoconstrictor and pro-inflammatory effects. AT2 receptors are present in the adrenal medulla, brain, and reproductive tissues. Furthermore, recent research suggests that AT2 receptors may counterbalance the effects of AT1 receptors by promoting vasodilation, anti-inflammatory responses, and tissue repair.

Relationship Between Angiotensin 1 and Angiotensin 2

• Angiotensinogen, a liver-derived protein, is enzymatically cleaved by renin to produce angiotensin I. Subsequently, angiotensin I is converted to angiotensin II by the action of angiotensin-converting enzyme (ACE).
• Both angiotensin I and angiotensin II are peptide hormones composed of amino acids.
• Moreover, both interact with specific receptors in the body.

Difference Between Angiotensin 1 and Angiotensin 2

Definition

Angiotensin I is a peptide hormone and an important component of the renin-angiotensin-aldosterone system (RAAS) in the human body. At the same time, angiotensin II is a potent hormone and a central component of the renin-angiotensin-aldosterone system (RAAS) in the human body.

Structure

While angiotensin I is a decapeptide composed of ten amino acids, angiotensin II is a shorter octapeptide consisting of eight amino acids.

Binding

Angiotensin I can bind to angiotensin type 1 (AT1) and angiotensin type 2 (AT2) receptors, although its affinity for these receptors is much lower compared to angiotensin II. However, angiotensin II primarily acts on AT1 receptors, leading to vasoconstriction and other physiological effects.

Biological Activity

Moreover, angiotensin I is relatively inactive and has limited biological activity than angiotensin II.

Receptor Binding

Angiotensin I has a lower affinity for angiotensin receptors compared to angiotensin II.

Conclusion

The main difference between angiotensin 1 and angiotensin 2 is that angiotensin I is relatively inactive and has a lower affinity for angiotensin receptors than angiotensin II.

Reference:

1. “Angiotensin I.” Encyclopedia Britannica.
2. “Angiotensin II receptor blockers.” Mayo Clinics.

Image Courtesy:

1. “2712 Renin Angiotensin System-01” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia