Renin Angiotensin System


The system of renin-angiotensin is basically attached with the generation of blood pressure by modulating the water reabsorption, vascular tone, sodium reabsorption and volume of blood. Their primary function is building resistance vessels, instigating the delivery of sodium at different levels, stimulating vascular and cardiac hypertrophy, and many others.

What is Renin?

Renins are defined as one of the most remarkable enzymes that are secreted by the kidneys of human beings. There are probabilities of being liberated by body placenta as well. The enzyme plays a very significant role in the complete physiological system, as it helps in the regulation of the blood pressure in the body.

When it is found in the blood of the human body the enzyme acts as one of the enzymes known as the angiotensinogen and it leads to the secretion of angiotensin I. Angiotensin I is among the very few products that are manufactured with the aid of the angiotensin-converting enzyme that separates the two amino acids from the ten amino acid chains of angiotensin I. Thus angiotensin II is formed.

Renin Function

The main function of the renin is the activation of the renin-angiotensin system, through the help of the angiotensinogen and its breakdown. The liver of the body produces it for the production of angiotensin I. The angiotensin I is then further transformed to angiotensin II, with the assistance of the angiotensin-converting enzyme. This kind of procedure takes place in the capillaries that are located in the lungs.

Angiotensin II is utilized for the constriction of the blood vessels. Thereupon it expands the release of the proper ADH and aldosterone. It stimulates the hypothalamus and activates the reflex of thirst. Every reflex leads to the expansion of the pressure of the blood. The basic function is an increase in the additional expansion of the pressure of the blood. It leads to restoration of the perfusion pressure that is seen in the kidneys.

The juxtaglomerular cells of the kidney maintain the perfusion pressure of the kidneys. It is done through the stretch receptors that are located in the vascular walls. The cells of juxtaglomerular secrete of the enzyme renin when stimulated by the macula densa.

Figure 1: Juxtaglomerular Apparatus of Kidney

The principal function of the macula densa is to understand the changes in the sodium level which goes to the distal tubule. It acts upon the sudden drop in the tubular sodium load and as a result stimulates the release of renin from the juxtaglomerular cells.

What is Angiotensin?

Angiotensin is illustrated as a protein that is secreted and generated by the liver. Kidney-produced enzyme renin converts this to Angiotensin I. Basically the hormone does not have any role but is a necessary precursor of Angiotensin II. Further processing in the circulatory system by the angiotensin-converting factor activity as it goes through the lungs and the kidneys for the generation of Angiotensin II. Angiotensin II has the cumulative influence of increasing the heart rate, complete hydration along with intake of salt. Some of the influences of angiotensin II can be felt through the blood vessels, nerves, kidneys, and others.

What is Renin-Angiotensin System (RAAS)?

The RAAS is a kind of system of hormone that is involved in arterial blood pressure regulation, and concentration of the sodium of plasma. On the liberation of the renin in the blood, it executes on angiotensinogen that undergoes the proteolytic cleavage for the enzyme decapeptide angiotensin I. Angiotensinogen is a circulating layer. Vascular endothelium possesses an enzyme known as the angiotensin transforming enzyme which splits into two amino acids and leads to the formation of angiotensin II and the other tissues in the body consisting of the heart, brain, and angiotensin II. The constitution of the system is ACE, renin, Angiotensin I, and II.

Figure 2: RAAS system

Functions of RAAS

The RAAS helps in the building of the resistance vessels, thereby expanding the arterial pressure and the systemic vascular resistance. The system aids in the stimulation of the delivery of the system at distinct sites of renal tubular and expands the retention of water of the body. It aids in instigating the liberation of the vasopressin from the posterior pituitary and expands the retention of the liquid by the kidneys. It aids in the stimulation of vascular and cardiac hypertrophy. It facilitates the release of norepinephrine from the sympathetic nerves and prevents the uptake of norepinephrine thereby optimizing the function of sympathetic adrenergic fibres.

Importance of RAAS

The RAAS system takes care of the blood pressure levels of the blood cells. In the fall or up of the blood pressure in a person, the system starts to function rapidly by the release of renin in the bloodstream. Hypertension and failure of heart are treated majorly by manipulative therapies. All ACE inhibitors and receptor blockers are created for reducing the arterial blood pressure, blood volume, ventricular afterload, and preload, along with vascular hypertrophy and reverse cardiac. The approaches of therapy motives for complete inhibition of RAAS provide more diagnostic advantage for patients with other renal and heart diseases.


Renin-angiotensin system is a kind of system of hormones that aids in the regulation of blood pressure, fluid, the balance of the electrolytes, and systemic vascular systems. The system aids in the expansion of arterial pressure and systemic vascular resistance. They are responsible for the regulation of sodium.


Q1. What is the renin enzyme?

Ans. Renin is a kind of enzyme that helps in the regulation of blood pressure and the maintenance of healthy levels of potassium and sodium in the body. Made by the special cells in the body, renin is secreted in the bloodstream when the level of blood pressure becomes low.

Q2. Does Angiotensin aid in controlling stress?

Ans. Angiotensin II or Ang II is a vital hormone of stress. Stress stimulates the circulation and the RAS of the brain via the formation and expansion of the Ang II AT1 receptor. The process of circulation and the tissue Ang II significantly expands in both the acute and chronically stressed animals.

Updated on: 13-Apr-2023


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