Reninomas are benign tumors originating from the cells of the juxtaglomerular apparatus. They produce excessive amounts of renin, leading to secondary hyperaldosteronism. As a consequence of this hormonal activation, patients develop severe hypertension, potassium wasting, and hypokalemia.

What causes increased renin secretion?

Increased renin release from the juxtaglomerular cells is caused by several conditions: reduction in renal blood flow from heart failure, blood loss, hypotension or ischemia of the kidneys, sodium diuresis (excessive sodium loss in urine), and beta-adrenergic stimulation.

Where do renin producing neoplasms occur?

The tumor usually arises from the juxtaglomerular cells of the kidney, and only 41 such cases were reported in the mid-1990s. Less frequently, non–juxtaglomerular cell renal tumors, as well as extrarenal renin-secreting tumors have been reported.

What cells releases renin?

The main source of renin is the juxtaglomerular cells (JGCs), which release renin from storage granules. Besides the renin-angiotensin system (RAS) in the JGCs, there exist local RASs in various tissues.

What is abnormal renin secretion?

A hypotensive response, or lack of it, to angiotensin-converting enzyme inhibitor is similarly informative. Because the normal kidney exposed to high arterial pressure and normal salt intake will reduce its renin secretion to near zero, any renin secretion in a hypertensive setting can be considered abnormal.

Renin Angiotensin Aldosterone System

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What is the role of angiotensinogen?

Angiotensinogen is a component of the renin-angiotensin system (RAS), a hormone system that regulates blood pressure and fluid balance. It is also known as the renin substrate, and is a non-inhibitory member of the serpin family of proteinase inhibitors (MEROPS inhibitor family I4, clan ID, MEROPS identifier I04.

Does renin cause vasoconstriction?

Renin enters the liver via the blood and converts angiotensinogen into angiotensin, which both stimulates the production of aldosterone by the adrenal cortex and directly causes vasoconstriction and a resulting increase in blood pressure.

How does juxtaglomerular cells release renin?

Juxtaglomerular cells secrete renin in response to a drop in pressure detected by stretch receptors in the vascular walls, or when stimulated by macula densa cells. ... These cells also respond directly to a decrease in systemic blood pressure which is manifested as a lower renal perfusion pressure.

When do juxtaglomerular cells secrete renin?

The juxtaglomerular cells, derived from smooth muscle cells, of the afferent arteriole secrete renin when blood pressure in the arteriole falls. Renin increases blood pressure via the renin-angiotensin-aldosterone system.

What stimulates granular cells to release renin?

The secretion of renin occurs when exocytosis of the granules is stimulated. The exocytosis of the granular cells is regulated by two main intracellular signaling molecules, cAMP which stimulates renin release and intracellular calcium ion concentration (Ca²⁺) which inhibits renin secretion.

How is reninoma diagnosed?

The diagnosis of reninoma is usually confirmed by cytoplasmic positivity for renin. Renin positivity may also be observed in some cases of Wilms' tumor (WT-1 staining), renal cell carcinoma (RCC), or renal oncocytoma.

How do you check renin levels?

Doctors usually test your levels of renin and aldosterone at the same time. They may call it a plasma renin activity test or an aldosterone-renin ratio. A technician will take a sample of your blood and send it to a lab. The test results will tell you if your renin and aldosterone levels are high, low, or normal.

Do JG cells secrete EPO?

EPO is expressed by interstitial fibro- blast-like cells of the renal cortex (7, 78, 113). In the adult kidney, renin is produced by juxtaglomerular (JG) cells that are located in the media layer of afferent arterioles at the entrance into the glomerulus (56, 151).

What activates renin release?

Renin is a proteolytic enzyme that is released into the circulation by the kidneys. Its release is stimulated by: sympathetic nerve activation (acting through β₁-adrenoceptors) renal artery hypotension (caused by systemic hypotension or renal artery stenosis)

What inhibits renin release?

Beta blockers inhibit renin release from the kidney and were the original renin-angiotensin system inhibitors. Reduced renin release leads to reduced concentrations of angiotensin I and II, which may contribute to the benefits of beta blockade in heart failure.

Where is angiotensinogen produced?

Angiotensinogen is produced in the liver and is found continuously circulating in the plasma. Renin then acts to cleave angiotensinogen into angiotensin I.

Which hormone is secreted by juxtaglomerular cells?

Renin is a hormone secreted by the juxtaglomerular cells of the kidney; it interacts with a plasma protein substrate to produce a decapeptide prohormone angiotensin I.

What does the macula densa secrete?

Macula densa cells in the distal nephron, according to the classic paradigm, are salt sensors that generate paracrine chemical signals in the juxtaglomerular apparatus to control vital kidney functions, including renal blood flow, glomerular filtration, and renin release.

When does macula densa release renin?

The macula densa participates in the regulation of renin release from juxtaglomerular granular cells. Renin secretion depends on NaCl delivery to and reabsorption by the macula-densa cells at the end of the TAL.

When is renin secreted?

The secretion of renin is stimulated by the following three factors: When a fall in arterial blood pressure is detected by pressure sensitive receptors (baroreceptors) in the arterial vessels. When a decrease in sodium chloride (salt) is detected in the kidney by the macula densa in the juxtaglomerular apparatus.

Which is secreted by the juxtaglomerular apparatus?

Renin is secreted by juxtaglomerular cells located in the afferent arteriole. At the cellular level, renin secretion is mediated by the fusion of renin-containing granules with the luminal membrane of the cell.

Do macula densa cells secrete renin?

The macula densa participates in the regulation of renin release from juxtaglomerular granular cells. Renin secretion depends on NaCl delivery to and reabsorption by the macula-densa cells at the end of the TAL.

Is renin a vasoconstrictor or vasodilator?

In this construct prorenin (renin I) is the vasodilator limb and renin (renin IT) is the vasoconstrictor limb of a long-term cardiovascular control system that regulates blood pressure and tissue perfusion.

How does renin angiotensin system regulate blood pressure?

The RAAS is a complex multi-organ endocrine (hormone) system involved in the regulation of blood pressure by balancing fluid and electrolyte levels, as well as regulating vascular resistance & tone. RAAS regulates sodium and water absorption in the kidney thus directly having an impact on systemic blood pressure.

What is the site of production of renin?

Sites of Renin Synthesis and Renin Secretion in the Kidney

In the adult kidney, renin is synthesized by myofibroblast-like cells that are located in the media layer of renal afferent arterioles at the entrance into the glomerular capillary network (Figure 1a).