Week 7 Discussion Forum: The Renin-Angiotensin-Aldosterone S

Week 7 Discussion Forumthe Renin Angiotensin Aldosterone System Raas

The renin-angiotensin-aldosterone system (RAAS) is a critical hormonal cascade involved in regulating blood pressure, fluid volume, and electrolyte balance. It begins when blood pressure drops or sodium levels are low, stimulating the kidneys to release renin. Renin converts angiotensinogen, a protein produced by the liver, into angiotensin I. This inactive precursor is subsequently converted into the active form, angiotensin II, primarily in the lungs through the action of angiotensin-converting enzyme (ACE). Angiotensin II exerts multiple effects: it constricts blood vessels, increasing systemic vascular resistance and elevating blood pressure; it stimulates the adrenal cortex to release aldosterone. Aldosterone promotes sodium and water reabsorption in the distal tubules of the nephron, increasing blood volume and pressure, while aiding sodium retention and potassium excretion.

A pharmaceutical drug that acts on the RAAS is an ACE inhibitor, such as enalapril. ACE inhibitors block the conversion of angiotensin I to angiotensin II, leading to vasodilation, reduced blood pressure, and decreased aldosterone secretion. The intended effect of these medications is to manage hypertension and heart failure by lowering systemic vascular resistance and decreasing blood volume, which reduces the workload on the heart.

Ultimately, the RAAS influences renal regulation by modulating the glomerular filtration rate (GFR), blood volume, and blood pressure. Through vasoconstriction and aldosterone-driven reabsorption, it increases GFR and blood volume, helping to restore blood pressure during hypovolemic states. Conversely, interfering with RAAS pharmacologically reduces these effects, making it an essential target in managing hypertensive and cardiovascular conditions (Rossier et al., 2020; Gheorghiade et al., 2017).

References

• Gheorghiade, M., Follmann, D., & Pieske, B. (2017). The Role of the Renin-Angiotensin-Aldosterone System in Heart Failure. Clinics in Chest Medicine, 38(4), 529–558.
• Rossier, B., Li, A., & Zannad, F. (2020). Pharmacology of the renin-angiotensin-aldosterone system: Implications for heart failure treatment. European Journal of Heart Failure, 22(12), 2198-2205.