You may have heard the term Angiotensin II before, especially if you or someone you know manages blood pressure or kidney health. But what does Angiotensin II do?
Angiotensin II is a small hormone that helps balance blood pressure and body fluids. It travels in the bloodstream and tells blood vessels to tighten, raising pressure. It also tells the kidneys to hold on to salt and water to boost blood volume.
Beyond pressure and fluids, it signals your heart, lungs, and nerves to coordinate how your body responds to stress and injury. In the following sections, you’ll learn what does Angiotensin II do, how it works, and why it matters for your health.
What is Angiotensin II?
Angiotensin II is an octapeptide hormone formed when the Angiotensin-Converting Enzyme (ACE) removes two amino acids from Angiotensin I. This conversion primarily occurs in the lungs, where ACE is abundant in blood vessel cells.
After its formation, Angiotensin II travels through the blood and tissues, binding to two main types of receptors: Angiotensin II Type 1 Receptor (AT₁) and Angiotensin II Type 2 Receptor (AT₂). The AT₁ receptor regulates blood pressure and fluid balance, while the AT₂ receptor can counteract some of these effects and promote cell growth and repair.
When your blood pressure drops or your body needs to hold on to more water and salt, Angiotensin II helps by narrowing your blood vessels and signaling your kidneys to save salt and water. This hormone acts quickly to keep your blood pressure safe and maintain the right amount of fluids in your body.
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How Angiotensin II works in the body
Angiotensin II is a peptide hormone that has a crucial role in maintaining blood pressure. It influences various functions that help maintain overall blood flow, pressure, and fluid balance, such as:
Regulation of blood pressure
One of the main jobs of Angiotensin II is to raise blood pressure when needed. It does this by tightening the muscles around your blood vessels. When these vessels get narrower, your blood pressure goes up. This helps ensure that your organs get enough blood and oxygen.
When Angiotensin II attaches to AT₁ receptors on blood vessels, it sets off a process that raises calcium levels inside muscle cells. This increase causes the muscles to tighten, which narrows the blood vessels (vasoconstriction).
The tighter vessels make blood flow harder, increasing pressure in your arteries. This increased pressure helps keep blood moving to vital organs when you lose fluids or are under stress.
Angiotensin II helps your adrenal glands release Aldosterone, a hormone that signals your kidneys to reabsorb sodium and water. This increases the fluid in your blood vessels, which raises blood pressure. Angiotensin II also adjusts how tight and full your circulatory system is by affecting both your blood vessels and kidneys.
However, if Angiotensin II is too active, it can cause blood pressure to stay high for too long. This is why some people with High Blood Pressure take medicines that block Angiotensin II.
Effects on the kidney
Angiotensin II also affects the kidneys in important ways. It helps control the amount of blood flowing through the kidneys and the amount of salt and water they store or release.
Angiotensin II helps control kidney filtration. When it narrows certain blood vessels in the kidney, it reduces blood flow but helps maintain the pressure to filter waste. This filtering process is called the Glomerular Filtration Rate (GFR). The Glomerular Filtration Rate checks how well your kidneys filter blood.
Additionally, it’s important to understand what Angiotensin II does to renal blood flow. Renal blood flow is the amount of blood that reaches the kidneys.
Angiotensin II also lowers total blood flow in the kidneys by tightening both blood vessels. This helps keep enough fluid filtered while preventing the loss of too much salt and water.
By promoting sodium and water retention, Angiotensin II raises blood pressure and ensures your body conserves vital fluids during dehydration or blood loss. However, if renal blood flow drops too much, it can harm the kidneys.
So, Angiotensin II carefully balances this to keep your body’s fluids and blood pressure in check. Additionally, it helps control urine production, further supporting fluid balance in the body. However, too much Angiotensin II can harm the kidneys over time by narrowing blood vessels too much.
Effects on the heart
Angiotensin II has several effects on the heart. It can raise blood pressure, making the heart work harder. It also causes heart muscle cells to grow or change over time.
Angiotensin II increases the heart’s ability to contract and beat faster by allowing more calcium into heart muscle cells. It also encourages the heart muscle to grow thicker, which can happen when the heart is stressed. This thickening is a way the heart tries to cope. Angiotensin II also helps regulate the release of hormones that affect heart function.
While this is helpful for short-term stress, having too much Angiotensin II for a long time can lead to harmful changes that occur in chronic Heart Failure. Increasing pressure and volume can strain the heart, but improving contractility helps it handle sudden demands.
Effects on the lungs
In the lungs, Angiotensin II can affect blood vessels and influence how blood flows through them. It may contribute to tightening the lung blood vessels, affecting breathing in some conditions. Angiotensin II also plays a role in inflammation and repair processes in lung tissue.
Your lungs produce most of your body’s ACE. This enzyme helps change Angiotensin I into Angiotensin II as blood flows through small vessels. In severe conditions like Acute Respiratory Distress Syndrome (ARDS), Angiotensin II can worsen lung damage by increasing inflammation and fluid buildup.
On the other hand, ACE2 is another enzyme that breaks down Angiotensin II into protective substances or peptides. Lower levels of ACE2 in the lungs are linked to more severe lung damage.
Interaction with the Sympathetic Nervous System
The Sympathetic Nervous System (SNS) controls your body’s ‘fight or flight’ response. Angiotensin II works closely with this system to raise blood pressure and heart rate when needed. It helps increase the release of certain chemicals that tighten blood vessels and make your heart beat faster. They prepare your body to respond to stress or danger by ensuring your organs get enough blood.
It boosts the release of Norepinephrine, a chemical that works as a neurotransmitter and a hormone. Angiotensin II also stops Norepinephrine from being returned to the nerve endings, leading to stronger blood vessel constriction during stress.
Therefore, Angiotensin II works on brain parts, like the paraventricular nucleus, to activate the body’s ‘fight or flight’ response. This helps raise blood pressure when you feel stressed. Angiotensin II and this system work together in a loop to keep blood pressure higher during stress.
After childbirth (Postpartum role)
After giving birth, a woman’s body undergoes many changes. Angiotensin II helps adjust blood pressure and fluid balance during this time and supports the body as it returns to normal after pregnancy. However, changes in Angiotensin II activity can sometimes affect blood pressure postpartum, so monitoring is essential.
Furthermore, after pregnancy, women, especially those with hypertensive (High Blood Pressure) disorders, become more sensitive to Angiotensin II. This increased sensitivity can lead to higher blood pressure after childbirth and may elevate long-term cardiovascular risk.
Animal studies show that blocking Angiotensin II type 1 receptor autoantibodies can improve postpartum blood pressure and heart function in Preeclamptic cases.
Preeclampsia: A severe pregnancy complication involving High Blood Pressure and liver/kidney damage.
What does an Angiotensin II Antagonist do
An Angiotensin II antagonist is a type of medicine that blocks the action of Angiotensin II. By doing this, it helps lower blood pressure and reduces the strain on the heart and kidneys. These medicines are often used to treat High Blood Pressure and protect kidney function.
As heart and blood pressure medications, Angiotensin II antagonists, also known as ARBs, block AT₁ receptors. This stops Angiotensin II from tightening blood vessels and increasing Aldosterone levels. As a result, ARBs lower blood pressure and reduce pressure on the heart and kidneys.
Doctors often prescribe ARBs when ACE inhibitors cause a cough or for patients with diabetic kidney disease. They help restore balance by preventing too much narrowing of blood vessels and fluid retention without impacting other hormones.
Conclusion
Angiotensin II is a powerful hormone that tightens blood vessels, boosts fluid retention, and tweaks organ function to keep your body stable during stress. It plays key roles in blood pressure control, kidney filtration, heart strength, lung health, and nerve signaling. After pregnancy, your body’s response to it can stay elevated, highlighting its lasting impact.
Medications that block Angiotensin II can effectively manage High Blood Pressure and protect your organs. Understanding what does Angiotensin II do can help you and your doctor make informed choices about cardiovascular and kidney health.
This information is for educational purposes and is not a substitute for medical advice. Always talk with your healthcare provider about diagnosis or treatment plans.
Frequently Asked Questions
What happens when Angiotensin II is blocked?
When you block Angiotensin II, your blood vessels relax and open wider. This helps your blood flow more easily and lowers your blood pressure. Blocking Angiotensin II also protects your heart and kidneys from damage. It can bring down your risk of heart attacks and strokes.
What happens when you have too much Angiotensin?
When you have too much Angiotensin, your blood vessels narrow, and your body holds on to extra water and salt. This raises your blood pressure. You may also keep more fluid in your body, and your heart can get bigger over time.
How does Angiotensin II contribute to inflammation?
Angiotensin II can inflame your body’s tissues. It makes blood vessels leakier and draws more immune cells to the area. It also helps release special signals called Cytokines that make swelling worse. This can lead to tissue damage and more inflammation in your body.
How does Angiotensin II contribute to tissue injury?
Angiotensin II can cause tissue injury by making your body produce more harmful molecules called free radicals and by increasing inflammation. It can also make blood vessels leaky and bring more immune cells to the area, hurting tissues and making them work less well over time.
What does Angiotensin II do to GFR?
Angiotensin II reduces blood flow in the kidneys but maintains pressure in the glomeruli to support filtration during low blood pressure. It narrows both the afferent and efferent arterioles, increasing pressure in the efferent arteriole and stabilizing the Glomerular Filtration Rate efficiently.
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