Cơ chế hoạt động của hệ thống Renin-Angiotensin-Aldosteron
The Renin-Angiotensin-Aldosterone System (RAAS) is a complex biological system that plays a crucial role in regulating blood pressure and fluid balance in the body. This system involves a series of biochemical reactions that result in the production of substances that constrict blood vessels and increase blood volume, thereby increasing blood pressure. Understanding the mechanism of action of this system is essential for the management of various cardiovascular diseases. <br/ > <br/ >#### The Initiation of the RAAS <br/ > <br/ >The Renin-Angiotensin-Aldosterone System is initiated when the kidneys detect a decrease in blood flow or a decrease in sodium concentration in the blood. In response to these stimuli, the kidneys release an enzyme called renin into the bloodstream. Renin acts on a protein called angiotensinogen, which is produced by the liver and released into the blood. The interaction between renin and angiotensinogen results in the formation of angiotensin I, a decapeptide. <br/ > <br/ >#### Conversion of Angiotensin I to Angiotensin II <br/ > <br/ >Angiotensin I is relatively inactive. However, it serves as a precursor to a much more potent substance, angiotensin II. The conversion of angiotensin I to angiotensin II is facilitated by an enzyme called angiotensin-converting enzyme (ACE), which is found predominantly in the lungs. Angiotensin II is a powerful vasoconstrictor, meaning it constricts blood vessels, thereby increasing blood pressure. <br/ > <br/ >#### The Role of Angiotensin II <br/ > <br/ >Beyond its vasoconstrictive properties, angiotensin II also stimulates the release of aldosterone, a hormone produced by the adrenal glands. Aldosterone acts on the kidneys, causing them to reabsorb more sodium and water from the urine back into the blood. This increases the volume of blood, which in turn increases blood pressure. Furthermore, angiotensin II stimulates the release of another hormone, vasopressin (also known as antidiuretic hormone), which also promotes water reabsorption in the kidneys. <br/ > <br/ >#### The Regulation of the RAAS <br/ > <br/ >The Renin-Angiotensin-Aldosterone System is regulated by a negative feedback mechanism. When blood pressure reaches a certain level, the production of renin is inhibited, which in turn reduces the production of angiotensin II and aldosterone. This leads to a decrease in blood volume and blood pressure, bringing the system back into balance. <br/ > <br/ >In conclusion, the Renin-Angiotensin-Aldosterone System is a vital regulatory system that maintains blood pressure and fluid balance in the body. It involves a series of biochemical reactions that result in the production of substances that constrict blood vessels and increase blood volume. Understanding the mechanism of action of this system is crucial for the management of various cardiovascular diseases.