Angiotensin 2 Gfr

Angiotensin II and Glomerular Filtration Rate (GFR): A Q&A Approach

Introduction:

Angiotensin II (Ang II) is a potent vasoactive peptide playing a crucial role in regulating blood pressure and fluid balance. Its impact on the glomerular filtration rate (GFR), the rate at which blood is filtered by the kidneys, is complex and multifaceted. Understanding this relationship is vital for managing various kidney diseases and hypertension. This article explores the intricate connection between Ang II and GFR through a question-and-answer format.

I. The Basics: What is the relationship between Angiotensin II and GFR?

Q: What is the primary function of Angiotensin II?

A: Ang II's primary function is to raise blood pressure. It achieves this through several mechanisms, including vasoconstriction (narrowing blood vessels), stimulating the release of aldosterone (a hormone that increases sodium and water reabsorption in the kidneys), and stimulating the release of antidiuretic hormone (ADH), which increases water reabsorption.

Q: How does Angiotensin II affect GFR?

A: The effect of Ang II on GFR is not straightforward. While it initially causes afferent arteriolar vasoconstriction (reducing blood flow to the glomerulus), it also simultaneously causes efferent arteriolar vasoconstriction (reducing blood outflow from the glomerulus). The net effect depends on the balance of these constrictions and other factors like systemic blood pressure. In many cases, the initial reduction in GFR is modest, allowing for some maintenance of filtration despite reduced renal blood flow.

II. The Complexities: Different Scenarios and Their Impact on GFR

Q: What happens to GFR in conditions of low blood pressure (hypotension)?

A: In hypotension, the renin-angiotensin-aldosterone system (RAAS) is activated to raise blood pressure. Ang II's vasoconstricting effects become crucial. Although initial afferent arteriolar constriction reduces GFR, the more significant efferent arteriolar constriction helps maintain glomerular capillary pressure, thereby preventing a drastic drop in GFR. This is a protective mechanism to preserve kidney function in the face of reduced blood flow.

Q: How does Ang II affect GFR in chronic kidney disease (CKD)?

A: In CKD, the kidneys are damaged, and their ability to filter blood is impaired. While initially, the RAAS might help maintain GFR, chronic activation of the system leads to sustained vasoconstriction, particularly in the efferent arteriole. This ultimately contributes to glomerular sclerosis (scarring), progressive loss of nephrons (functional units of the kidney), and further decline in GFR, accelerating CKD progression.

Q: What is the role of Angiotensin-Converting Enzyme (ACE) inhibitors and Angiotensin Receptor Blockers (ARBs) in managing GFR?

A: ACE inhibitors and ARBs are medications that block the RAAS, reducing Ang II levels. By inhibiting Ang II's vasoconstricting effects, these drugs help prevent further decline in GFR, particularly in CKD. They reduce the pressure within the glomerulus, protecting it from further damage. This is a key reason for their widespread use in managing hypertension and CKD. For example, in patients with diabetic nephropathy (kidney damage due to diabetes), ACE inhibitors and ARBs are frequently prescribed to slow the progression of kidney disease and protect GFR.

III. Clinical Implications and Treatment Strategies

Q: How is GFR measured, and how is Ang II's impact assessed clinically?

A: GFR is estimated using serum creatinine levels and equations like the eGFR (estimated glomerular filtration rate) formula. The impact of Ang II is indirectly assessed through blood pressure monitoring, urine analysis (for proteinuria, a marker of kidney damage), and imaging studies of the kidneys. In some research settings, direct measurements of renal blood flow and glomerular pressure are used.

Q: Are there any situations where the effects of Ang II on GFR are beneficial?

A: While often detrimental in chronic conditions, the initial vasoconstriction caused by Ang II can be beneficial in acute situations like hemorrhage (severe blood loss). The efferent arteriolar vasoconstriction helps maintain glomerular capillary pressure and prevents a catastrophic drop in GFR, ensuring some degree of filtration continues even under critically low blood pressure conditions.

IV. Conclusion

Angiotensin II's influence on GFR is complex, involving a delicate balance of afferent and efferent arteriolar vasoconstriction. While it might initially help maintain GFR in situations of low blood pressure, its chronic activation in conditions like CKD accelerates kidney damage and leads to GFR decline. Blocking Ang II using ACE inhibitors and ARBs is a cornerstone of managing hypertension and CKD, effectively protecting GFR and slowing disease progression.

V. FAQs:

1. Q: Can high Ang II levels directly damage the glomeruli? A: Yes, sustained high levels of Ang II can contribute to glomerular damage through multiple mechanisms, including oxidative stress, inflammation, and mesangial cell proliferation (leading to scarring).

2. Q: Are there other factors besides Ang II that affect GFR? A: Absolutely. Factors like blood pressure, fluid volume, renal blood flow, and the integrity of the glomerular filtration barrier all significantly influence GFR.

3. Q: Can ACE inhibitors and ARBs cause a sudden drop in GFR? A: While rare, this is possible, particularly in patients with severe renal artery stenosis (narrowing of the renal arteries). Careful monitoring is essential when initiating these medications.

4. Q: What are the side effects of ACE inhibitors and ARBs? A: Common side effects include cough (ACE inhibitors), dizziness, and hyperkalemia (high potassium levels).

5. Q: How often should GFR be monitored in patients taking ACE inhibitors or ARBs? A: The frequency of monitoring depends on the individual patient's risk factors and baseline GFR. Regular monitoring, at least annually, is often recommended, especially in those with CKD.

Search Results:

Effect of angiotensin II infusion on the human glomerular Angiotensin II (ANG II) infusion has been reported to impair barrier size selectivity and exacerbate proteinuria in the rat. To examine whether this is also true of humans, we infused a pressor dose of ANG II into seven healthy controls and seven nephrotic patients.

Angiotensin II and the maintenance of GFR and renal blood flow … The intrarenal effects of angiotensin II restore GFR back to normal within one to two weeks, by which time circulating plasma angiotensin II levels are no longer elevated. In contrast to its effects on GFR, angiotensin II has minimal effects on renal blood flow after stenosis.

Glomerular actions of angiotensin II - PubMed 31 May 1984 · Angiotensin II regulates whole kidney glomerular filtration rate by influencing one or more of the determinants of single nephron glomerular filtration rate, particularly the ultrafiltration coefficient and glomerular plasma flow rate.

Role of arterial hypertension and angiotensin II in chronic kidney ... 16 Feb 2023 · Ang II decreases renal blood flow and decreases the GFR, exerting effects both on renal microvasculature and on the glomerular mesangium. Ang II predominantly contracts preglomerular arterioles. When the pre- and post-glomerular resistance increases in parallel, the outcome is an increased GFR.

Angiotensin actions in the kidney: Renewed insight into the angiotensin II receptor antagonist, saralasin, increased GFR in association with amelioration in the markedly low level of K1 without appreciably affecting arteriolar resistances [39].

Angiotensin II Blockade and Renal Protection - PMC 2-1-2. GFR. Responses of GFR to an ARB have been highly variable . Intrarenal infusion of a subpressor dose of an ARB significantly increased whole kidney GFR in dogs. Most clinical studies have also shown that the GFR remains stable when an ARB is administered.

Angiotensin II - StatPearls - NCBI Bookshelf 26 May 2023 · Angiotensinogen, an alpha-globulin, and the peptide prohormone is synthesized primarily by the liver and circulates in plasma. Angiotensin II (AT-II) has recently received FDA approval for use in patients in shock.

Effects of Angiotensin-II on GFR - medicowesome.com 17 Jun 2017 · The net effect of preferential rise in efferent arteriolar resistance is that the glomerular pressure is increased or stabilized(in hypoperfusion states), which helps to maintain or increase GFR.

UpToDate 4 Feb 2025 · The effect of angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) on kidney function in the patient with hypertension is related both to the glomerular actions of angiotensin II and the mechanism of autoregulation of the glomerular filtration rate (GFR) .

An educational tool to improve understanding of angiotensin II … 23 Oct 2019 · Hydrostatic capillary pressure is the primary biophysical determinant of the GFR, and it is transmitted to the renal circulation from the systemic arterial pressure.

Angiotensin II - an overview | ScienceDirect Topics 7.12.3.4.1 Regulation of GFR. Angiotensin II plays an important role in the regulation of GFR and renal blood flow (Ichikawi and Harris 1991) by constricting the efferent and afferent glomerular arterioles (Heyeraas and Aukland 1987; Myers et al. 1975; Yuan et al. 1990).

Role of arterial hypertension and angiotensin II in chronic kidney ... Ang II decreases renal blood flow and decreases the GFR, exerting effects both on renal microvasculature and on the glomerular mesangium. Ang II predominantly contracts preglomerular arterioles. When the pre- and post-glomerular resistance increases in parallel, the outcome is an increased GFR.

Angiotensin II type 2 receptor in chronic kidney ... - Kidney … 2 May 2009 · Angiotensin II is believed to mediate blood pressure-independent progressive renal damage in chronic kidney disease (CKD).

Renal hemodynamic and tubular effects of angiotensins II and III Systemic infusion of ANG II produces dose-dependent decreases in renal blood flow (RBF), glomerular filtration rate (GFR) and filtration coefficient, and increases in filtration fraction. Intrarenally generated ANG II is also critical to alterations in …

Angiotensin - Wikipedia Angiotensin II is a sensitizer to tubuloglomerular feedback, preventing an excessive rise in GFR. Angiotensin II causes the local release of prostaglandins, which, in turn, antagonize renal vasoconstriction.

Angiotensin II: The Renal Hemodynamic Regulator in Glomerular … Explore the multifaceted roles of angiotensin II (Ang II) in glomerular filtration rate regulation and renal hemodynamics, unraveling its pathophysiological significance and therapeutic implications in renal disorders and hypertension.

Regulation of glomerular filtration rate and sodium excretion by ... Angiotensin II (AngII) helps to prevent excessive decreases in GFR in different physiological and pathophysiological conditions by preferentially constricting the efferent arterioles, an action that can be mediated by either intrarenally formed or circulating AngII.

Control of glomerular filtration rate by circulating angiotensin II After 90 min of infusion of the angiotensin-converting enzyme inhibitor SQ 14225, which presumably inhibited formation of both circulating and intrarenal ANG II, reduction of RAP to 81 +/- 2 mmHg resulted in marked decreases in GFR, filtration fraction (FF), and calculated efferent arteriolar resistance (RE), whereas renal blood flow (RBF) was ...

Role of the renin-angiotensin system in the regulation of Angiotensin II (Ang II) controls renal plasma flow, which depends on perfusion pressure and on renal vascular resistances; the glomerular filtration rate of single nephrons (SNGFR) also depends on these two parameters.

Hypertension: Angiotensin-II receptor blockers - CKS | NICE Use of angiotensin-II receptor blockers (ARBs) is contraindicated in: People with diabetes mellitus, or with an estimated glomerular filtration rate (eGFR) less than 60 mL/minute/1.73 m 2, who are also taking aliskiren. Pregnant women and …

Angiotensin 2 Gfr

Angiotensin II and Glomerular Filtration Rate (GFR): A Q&A Approach

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