In: Anatomy and Physiology
Like all viral pathogens, severe acute respiratory syndrome coronavirus 2, or SARS-CoV 2, requires a cell surface receptor in order to invade a given host cell. For SARS-CoV 2, this receptor is actually the enzyme Angiotensin Converting Enzyme 2, or ACE2. ACE2 is responsible for downregulation of the Renin-Angiotensin-Aldosterone System by deactivation of Angiotensin II. Explain the RAAS in detail, including the roles played by kidneys and the lungs, and then explain what effects using recombinant human ACE2, or rhACE2, to treat acute respiratory distress syndrome could have on blood pressure.
The Renin-Angiotensin-Aldosterone System (RAAS) is a hormone system in the body that plays a key role in the regulation of blood pressure and fluid balance. The system is mainly comprised of the three hormones renin, angiotensin II and aldosterone.
The first stage of the RAAS is the release of the enzyme renin.
Renin is released from the cells of the renal juxtaglomerular apparatus (JGA cells) in response either of these factors:
The cells in the JGA convert prorenin into renin and secrete it directly into the circulation.
The release of renin is inhibited by atrial natriuretic peptide (ANP), which is released by stretched atria in response to increases in blood pressure.
The renin converts the angiotensinogen, released by the liver, to angiotensin 1. Angiotensin I is then converted to angiotensin II by the angiotensin-converting enzyme (ACE) found on the surface of vascular endothelial cells, mainly in the lungs. Angiotensin II is a potent vasoconstrictor that causes the constriction of blood vessels and increases the blood pressure.
Angiotensin II stimulates the secretion of the aldosterone from the adrenal cortex.Aldosterone acts on the principal cells of the collecting ducts and increases the reabsorbtion of urinary sodium.This also increases the reabsorption of water from the collecting ducts.It promotes the excretion of the pottasium ions and this changes increases the volume of extracellular fluid in the body, which inturn increases blood pressure.
When we use recombinant human ACE2, or rhACE2, to treat acute respiratory distress syndrome , rhACE2 has the ability to counteract the hypertensive action of the angiotensin II. It produces Angiotensin 1-7 in mote quantities which causes a shortage of substrates for the Angiotensin II formation.They also prevent the action of angiotensin II and thus lowers the blood pressure.