How does angiotension 2 affect kidney?

Angiotensin 2 (Ang II) is a potent vasoconstrictor and plays a significant role in regulating blood pressure and fluid balance in the body. It affects the kidneys in several ways:

1. Renal Vasoconstriction:

Ang II causes vasoconstriction of the renal arteries and afferent arterioles, which leads to decreased blood flow to the kidneys. This reduced blood flow can impair kidney function and lead to a decrease in the glomerular filtration rate (GFR), the rate at which blood is filtered in the kidneys.

2. Sodium Retention:

Ang II stimulates the reabsorption of sodium and water in the proximal convoluted tubules and collecting ducts of the nephrons. This increased sodium reabsorption leads to an increase in extracellular fluid volume and can contribute to hypertension.

3. Activation of the Renin-Angiotensin-Aldosterone System (RAAS):

Ang II plays a central role in the activation of the RAAS. When blood pressure decreases or sodium levels decrease, the renin-angiotensin system is activated, leading to the release of renin from the kidneys, which in turn converts angiotensinogen into angiotensin I. Angiotensin-converting enzyme (ACE) then converts angiotensin I into Ang II. Ang II then stimulates the release of aldosterone from the adrenal glands, which further increases sodium reabsorption and fluid retention.

4. Glomerular Changes:

Chronic exposure to high levels of Ang II can cause structural changes in the kidneys, including thickening of the glomerular basement membrane, mesangial cell proliferation, and glomerulosclerosis. These changes can lead to progressive kidney damage and loss of kidney function.

5. Tubulointerstitial Changes:

Prolonged Ang II exposure can also lead to tubulointerstitial fibrosis and inflammation. The increased pressure and reduced blood flow in the kidneys can cause damage to the tubular cells and the surrounding interstitium, leading to scarring and impaired kidney function.

Therefore, Ang II has both acute and chronic effects on the kidneys, influencing renal blood flow, sodium handling, and the progression of kidney disease. Medications that block the effects of Ang II, such as ACE inhibitors or angiotensin receptor blockers (ARBs), are commonly used in the treatment of hypertension and chronic kidney disease to improve kidney function and prevent further damage.