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Intrarenal control of renal function is by tubuloglomerular feedback and by glomerulotubular balance. In tubu- loglomerular feedback, Na/Cl delivery to the. Tubuloglomerular feedback is an adaptive mechanism that links the rate of glomerular . Intrinsic—Tubuloglomerular Feedback and Glomerulotubular Balance. Glomerulotubular Balance refers to the phenomenon whereby a constant layer of protection if mechanisms of tubuloglomerular feedback, that normalize rates.

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This page was last edited on 16 Decemberat A Cellular And Molecular Approach. Factors that increase TGF sensitivity include: From Wikipedia, the free encyclopedia.

Tubuloglomerular Feedback and Glomerulotubular Balance

Journal of Mathematical Biology. Renal blood flow Ultrafiltration Countercurrent exchange Filtration fraction. The agents are vasoactive substances that alter either the magnitude or the sensitivity of the TGF response.

An increase in filtration at the glomerulus enhances filtrate reabsorption at the peritubular capillaries.

Efferent arterioles appear to play a lesser role; experimental evidence supports both vasoconstriction and vasodilation, with tubulogpomerular the former in the lower range and the latter in the higher range of NaCl concentrations 2.

Intrarenal control of renal function is by tubuloglomerular feedback and by glomerulotubular balance. Constricting the smooth muscle cells in the afferent arteriole, results in a reduced concentration of chloride at the MD.

Physiology of the kidneys and acid-base physiology. A high protein diet affects the feedback activity tubu,oglomerular making the single nephron glomerular filtration rate higher, and the Na and Cl concentrations in early distal tubule fluid lower. Extracellular adenosine contributes tubuloglomerulwr the regulation of GFR. Secretion clearance Pharmacokinetics Clearance of medications Urine flow rate.

The macula densa’s position enables it to rapidly alter afferent arteriolar resistance in response to changes in the flow rate through the distal nephron.

This signal is transmitted to the afferent arteriole. Compliance Vascular resistance Pulse Perfusion. Tubuloglomerular feedback adjusts GFR to maintain a relatively constant rate of distal tubule NaCl delivery.

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The American Journal of Physiology. Distal tubule NaCl delivery is proportionate to glomerular filtration rate. Skip to main content.

It involves the concept of purinergic signalingin which an increased distal tubular sodium chloride concentration causes a basolateral release of adenosine from the macula densa cells. The afferent arteriole dilates, which increases glomerular capillary pressure. The afferent arteriole cells release renin, leading to intrarenal angiotensin II formation. In other words, if the GFR spontaneously increases, the rate of water and solute resorption in the tubule proportionally increases, thus maintaining the same fraction the filtered load being resorbed.

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The size of the TGF response is directly dependent upon these changes. Journal of the American Society of Nephrology. A drop in arterial blood pressure causes both a decrease in GFR and a decrease in renal blood flow. By using this site, you agree to the Terms of Use and Privacy Policy. Tubuloglomerular feedback is one of several mechanisms the kidney uses to regulate glomerular filtration rate GFR. Excluding loop diuretic use, the usual situation that causes a reduction in reabsorption of NaCl via the NKCC2 at the macula densa is a low tubular lumen concentration of NaCl.

A large sodium chloride concentration is indicative of an elevated GFR, while low sodium chloride concentration indicates a depressed GFR.

TGF can stabilizes the fluid and solute delivery into the distal portion of the loop of Henle and maintain the rate of filtration near its ideal value using these mechanisms.

Glomerulotubular Balance | Pathway Medicine

The threshold at which the loop of Henle flow rate initiates feedback responses is affected. Copyright by Pathway Medicine Terms of Use. Distal segments of tubuoglomerular nephron have a very limited capacity to increase tubular resorption of water and solutes; consequently, a large increase in distal flow rates would result in a catastrophic loss of fluid in the urine.

The mechanistic basis of glomerulotubular balance is poorly understood but appears to act completely independently of neuroendocrine regulatory mechanisms and is likely an intrinsic property of the nephron itself. This initiates a cascade of events that ultimately brings GFR to an appropriate level. Active transepithelial transport is used by the thick ascending limb TAL cells to pump NaCl to the surrounding interstitium from luminal fluid. Reduced NaCl uptake via the NKCC2 at the macula densa leads to increased renin release, which leads to restoration of tubuooglomerular volume, and to dilation of the afferent arterioles, which leads to increased renal plasma flow and increased GFR.


Fluid flow through the nephron must be kept within a narrow range for normal renal function in order to not compromise the ability of the nephron to maintain salt and water balance. The TGF mechanism is a negative feedback loop in which the chloride ion concentration is sensed downstream in the nephron by the macula densa MDcells in the tubular wall near the end of TAL and the glomerulus.

The kidney maintains the tubluoglomerular concentrations, osmolality, and acid-base balance of blood plasma within the narrow limits that are compatible with effective cellular function; and the kidney participates in blood pressure regulation and in the maintenance of steady whole-organism water volume [4].

Extracellular adenosine activates A1 receptors on vascular afferent arteriolar smooth muscle cells, resulting in vasoconstriction and a reduction in GFR Schnermann et al. The macula densa is a collection of densely packed epithelial cells at the junction of the thick ascending limb TAL and distal convoluted tubule DCT. The macula densa uses the composition of the tubular fluid tubuloglomerulaf an indicator of GFR.

The muscle tension in the afferent arteriole is modified based on the difference between the sensed concentration and a target concentration. Significance Glomerulotubular balance is a critical mechanism which protects distal segments of the nephron from being overloaded in contexts of short-term increases in GFR.