How Does Renin Regulate Blood Pressure and Kidney Function?
Renin is one of the main enzymes that is secreted by our kidneys. Also, there is a chance that it might be secreted by the placenta of the body. This enzyme is a very important part of the entire physiological system and it helps in the controlling of the blood pressure in the body.
When found in the blood of the human body renin acts on one particular protein that is called angiotensinogen and that results in the releasing of the angiotensin I.
Angiotensin I is one of the few products that is produced with the help of the angiotensin-converting enzyme, which again splits the 2 amino acids from all the 10-amino-acid chains of angiotensin I. This, in turn, leads to the formation of angiotensin II. Students need to learn a bit more about the renin function and much more. So, we are here to provide some details on that.
What is Renin Enzyme?
Most students need to have some idea about renin meaning and that is exactly what we are going to write here. We all are familiar with renin as an enzyme that acts on angiotensinogen in order to produce the resultant products such as hypertension and others. It also helps in the control of blood pressure and systolic pressure as well. It is said that Angiotensin II is definitely one of the few active vasoconstrictors and that it is very potent as well. So, there is an increase in the secretion of aldosterone and cortisol from the direct action that happens in the adrenal cortex. The discovery of the renin hormone function happened in 1898 by Per Bergman and Robert Tigerstedt.
What is Renin Structure?
Renin has a primary structure that consists of about 406 amino acids in total. There are pre-and pro- segments that carry about 20 as well as 46 amino acids. The mature renin has about 340 amino acids and the total mass is about 37 kDa. Renin is produced by the kidney and sometimes the placenta and that is responsible for many functions as well. We are going to learn more about the secretion and functions of renin right now.
Students need to ensure that they have more information on the renin enzyme so that they can get a deeper understanding of the subject and can score good marks in the examination.
Secretion of Renin Hormone
The mural cells present in the afferent arterioles as well as the similar microvessels that are included in the kidney are the ones responsible for the secretion of the renin enzyme. These specialized cells are contained in the juxtaglomerular apparatus. When there is a decrease in our arterial blood pressure (this could be due to a prompt decrease in the volume of the blood), it is detected properly by baroreceptors (these are the pressure-sensitive cells). That is one of the most direct and causal links that stands between our blood pressure and the secretion of renin (there are some other methods that tend to operate via some longer pathways).
Renin Function
When we are talking about the renin function, there is a lot that the students need to know about. Renin is responsible for activating the renin–angiotensin system with the help of the process of cleaving angiotensinogen. This is produced by our liver, in order to yield angiotensin I. The angiotensin I is then further converted to form angiotensin II with the help of ACE also known as the angiotensin–converting enzyme. This process happens primarily within all the capillaries that are situated in the lungs.
Angiotensin II is then used to constrict all the blood vessels. It then increases the secretion of proper ADH as well as aldosterone. This in turn stimulates the hypothalamus and activates the thirst reflex. Each reflex then leads to an increase in our blood pressure. The primary function of the renin enzyme is basically to cause an additional increase in blood pressure. This then leads to the restoration of our perfusion pressure which is seen in the kidneys.
The juxtaglomerular kidney cells are responsible for the secretion of renin, which senses changes in the renal perfusion pressure. This is done via stretch receptors that are located in our vascular walls. These juxtaglomerular cells are also properly stimulated in order to provide a release of the enzyme renin by signaling in a prompt manner from our macula densa.
The main function of macula densa is to sense certain changes that happen in the sodium delivery that goes to our distal tubule. It then responds to a sudden drop in the tubular sodium load that is caused by the stimulation of renin release happening in these juxtaglomerular cells. If put together, the juxtaglomerular cells and the macula densa constitute the entire juxtaglomerular complex.
FAQs on Renin: Structure, Function, and Importance in Biology
1. What exactly is renin and what does it do in the body?
Renin is a special enzyme produced primarily by the kidneys. Its main job is to kickstart a process that helps regulate the body's blood pressure and maintain its fluid and salt balance. Think of it as the first domino in a chain reaction designed to keep your blood pressure stable.
2. What is the main function of renin specifically in the kidneys?
In the kidneys, renin is released by specialized cells called juxtaglomerular cells. These cells act like sensors. When they detect a drop in blood pressure or low sodium levels, they release renin into the bloodstream. This release signals the start of the Renin-Angiotensin-Aldosterone System (RAAS), which works to bring the blood pressure back up to normal.
3. How is renin different from rennin? Are they related?
No, they are not related and have very different functions. This is a common point of confusion.
- Renin (with one 'n') is the enzyme from the kidneys that controls blood pressure.
- Rennin (with two 'n's'), also called chymosin, is a digestive enzyme found in the stomachs of infant mammals, including humans, that helps digest milk protein.
4. Is renin considered an enzyme or a hormone?
Renin is technically classified as an enzyme because its primary role is to catalyse a chemical reaction: converting angiotensinogen into angiotensin I. However, it acts much like a hormone because it is secreted into the bloodstream to travel and act on substances far from its origin in the kidney. So, it's an enzyme that functions as part of the body's hormonal system.
5. How does renin actually help control our blood pressure?
Renin controls blood pressure through a sequence of events called the RAAS pathway:
- When blood pressure drops, the kidneys release renin.
- Renin converts a protein in the blood called angiotensinogen into angiotensin I.
- Another enzyme converts angiotensin I into angiotensin II.
- Angiotensin II is the powerful active substance that raises blood pressure by constricting blood vessels and stimulating the release of another hormone, aldosterone, which makes the body retain salt and water.
6. What triggers the kidneys to release renin into the bloodstream?
The kidneys are triggered to release renin by three main signals:
- A direct drop in blood pressure in the arteries of the kidney.
- Low sodium chloride (salt) levels in the kidney tubules, which is sensed by a structure called the macula densa.
- Stimulation from the sympathetic nervous system, which is part of the body's 'fight-or-flight' response.
7. Does renin directly cause blood vessels to tighten?
No, renin itself does not directly tighten or constrict blood vessels. This is a common misconception. Renin's role is to initiate the chemical reaction. The substance that is directly responsible for constricting blood vessels is angiotensin II, which is produced a few steps down the line in the pathway that renin started.
