Goldblatt Mechanism – Causes and Effects
The Goldblatt mechanism describes how reduced blood flow to the kidney activates the renin-angiotensin-aldosterone system, leading to high blood pressure.
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The Goldblatt mechanism describes how reduced blood flow to the kidney activates the renin-angiotensin-aldosterone system, leading to high blood pressure.
What Is the Goldblatt Mechanism?
The Goldblatt mechanism is a physiological and pathophysiological process in which reduced blood supply to the kidney triggers activation of the renin-angiotensin-aldosterone system (RAAS), ultimately causing an increase in blood pressure. This principle was first demonstrated in the 1930s by the American physiologist Harry Goldblatt, who experimentally constricted the renal artery in dogs and consistently produced sustained hypertension.
Causes and Triggers
The Goldblatt mechanism is set in motion whenever blood flow to one or both kidneys is chronically reduced. Common underlying causes include:
- Renal artery stenosis: Narrowing of the renal artery, most often caused by atherosclerotic plaques or fibromuscular dysplasia
- Chronic kidney disease with impaired renal perfusion
- Vascular occlusions or compressions affecting the renal arteries
- Aortic coarctation (a congenital narrowing of the main aorta) that reduces blood flow to the kidneys
Mechanism of Action
The Goldblatt mechanism proceeds through several well-defined steps:
- Reduced renal perfusion is sensed by specialized pressure-sensitive cells in the juxtaglomerular apparatus of the kidney.
- In response, these cells secrete increased amounts of the enzyme renin.
- Renin cleaves the circulating plasma protein angiotensinogen (produced by the liver) into angiotensin I.
- Angiotensin I is converted into the biologically active angiotensin II by the angiotensin-converting enzyme (ACE), which is mainly found in the lungs.
- Angiotensin II raises blood pressure through two main actions: it causes direct vasoconstriction (narrowing of blood vessels) and stimulates the release of aldosterone from the adrenal cortex.
- Aldosterone acts on the kidneys to promote sodium and water reabsorption, expanding blood volume and further elevating blood pressure.
Clinical Significance
The Goldblatt mechanism is the underlying basis of renovascular hypertension – a form of secondary hypertension caused by an identifiable organic cause. This type of hypertension is clinically important because it is often resistant to standard antihypertensive medications and requires targeted treatment. It is more common in older patients with atherosclerosis and in younger women with fibromuscular dysplasia.
Variants of the Goldblatt Model
Two classical experimental models have been described:
- Goldblatt 2K1C model (two-kidney, one-clip): Only one renal artery is clipped. The other kidney remains unaffected and can still excrete excess fluid. The RAAS remains chronically activated, driving persistent hypertension.
- Goldblatt 1K1C model (one-kidney, one-clip): The single existing kidney is clipped. In this model, hypertension is primarily volume-dependent, since no second kidney is available to compensate for fluid retention.
Diagnosis of Renovascular Hypertension
Since the Goldblatt mechanism underlies renovascular hypertension, the following diagnostic approaches are used:
- Doppler ultrasound of the renal arteries: Detection of stenosis through altered blood flow velocities
- CT angiography or MR angiography: Imaging of the renal arteries to visualize narrowing
- Plasma renin activity: Laboratory measurement of elevated renin levels in the blood
- Captopril renography: A functional scintigraphy test assessing renal perfusion under ACE inhibition
Treatment
Treatment of renovascular hypertension caused by the Goldblatt mechanism depends on the underlying cause:
- Interventional procedures: Percutaneous transluminal angioplasty (PTA) with or without stent placement to widen the narrowed renal artery
- Surgical therapy: Vascular reconstruction for complex or non-amenable stenoses
- Medical management: ACE inhibitors and angiotensin receptor blockers (ARBs) specifically target the RAAS and are effective antihypertensive agents. However, caution is warranted in bilateral renal artery stenosis, as ACE inhibitors can critically impair kidney function in this setting.
References
- Goldblatt H. et al. - Studies on Experimental Hypertension. Journal of Experimental Medicine, 1934.
- Kaplan N.M., Victor R.G. - Kaplan's Clinical Hypertension. 11th Edition. Lippincott Williams and Wilkins, 2015.
- Textor S.C. - Renovascular Hypertension and Ischemic Nephropathy. In: Brenner and Rector's The Kidney. 10th Edition. Elsevier, 2016.
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Related search terms: Goldblatt Mechanism + Goldblatt Effect + Goldblatt Hypertension