Introduction

Renin refers to an enzyme that helps in controlling blood pressure. It is released by special cells in the kidneys. When the blood pressure drops too low, or the body doesn’t have enough salt, this enzyme is released into the bloodstream. 

Biochemistry of Renin

There are 406 amino acids in the primary structure of the renin precursor. This precursor is characterised by a pre- and pro-segment that carry amino acids 20 and 46, respectively. The mass of mature renin is 37 kDa, and it has 340 amino acids. 

The secretion of this enzyme takes place by pericytes in the vicinity of various arterioles as well as by kidney microvessels. In particular, the juxtaglomerular cells produce this enzyme in response to three types of stimuli which are as follows:

• A reduction in arterial blood pressure. This reduction could be due to a reduction in blood volume. Pressure-sensitive cells known as baroreceptors can detect a reduction in arterial blood pressure. 
• A reduction in sodium load being delivered to the distal tubule. The measurement of load takes place by the macula densa of the juxtaglomerular apparatus.
• Sympathetic nervous system activity. This is responsible for controlling blood pressure. 

The secretion of this enzyme in humans takes place through two cellular pathways. One pathway is for the precursor pro renin secretion. Another pathway is for mature renin secretion.

What Is the Renin Test

The renin test is a test that facilitates the measurement of the amount of this enzyme in the blood. This test is applicable for both types of renin. For its measurement, a technician takes a blood sample for testing in a laboratory. 

The test results will reveal whether the levels of renin and aldosterone are high or low. High or low levels may reveal the reason why a person is suffering from high blood pressure:

• If this enzyme is high with normal aldosterone- This may be an indication of sensitivity to salt.
• If this enzyme is low with high aldosterone- This may be an indication of the improper functioning of the adrenal glands.
• If both are high- This may be an indication of kidney problems. 

The results of this test are helpful for a healthcare expert to make a decision on the type of treatment options or medication to give to a particular patient. 

Why Renin Test Is Performed

The measurement of Plasma Renin Activity (PRA) takes place as part of diagnosing and treating hypertension. Those who suffer from primary hyperaldosteronism will have a higher than normal aldosterone level. In contrast, patients who suffer from secondary hyperaldosteronism will have increased plasma levels of renin and aldosterone. 

Those who suffer from hypertension may get their renin and aldosterone levels analysed. Based on the levels of these two, healthcare experts would be able to select the correct treatment option for the patients.

Renin-Angiotensin System

The Renin-Angiotensin System (RAS) refers to a related group of hormones that is responsible for regulating blood pressure and controlling inflammation. The reason experts call it a system is due to the fact that each component impacts the other. Most importantly, all the parts are required for the proper functioning of the body. 

This system is a crucial part of the blood pressure regulatory system of the body. In particular, this takes place via the classical pathway of the renin-angiotensin-aldosterone system (RAAS).

Unsuitable activation of the classical pathway may lead to harmful effects like hypertension and vascular diseases. This system also promotes anti-inflammatory responses via its alternative renin-angiotensin pathway.

Conclusion

Renin is an enzyme that facilitates the management and control of blood pressure. Special cells in the kidneys are responsible for its secretion. When studying this enzyme, it is important to understand the renin test and the reason why it is performed.