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28-466: [REDACTED] Look up tgf in Wiktionary, the free dictionary. TGF may refer to: Medicine [ edit ] Tubuloglomerular feedback , a reflex of the nephrons in the kidney Transforming growth factor , either of two classes of polypeptide growth factors (TGF-α and TGF-β) Science [ edit ] Terrestrial gamma-ray flash ,

56-848: A burst of gamma rays produced in the Earth's atmosphere, generally associated with lightning Tidal Generating Force , an effect of gravity responsible for creating tides Trivial Graph Format , a text-based file format for describing graphs Entertainment [ edit ] The Games Factory , video game development software created by Clickteam The Gracious Few , an American rock group from York, Pennsylvania TGFbro , British YouTube duo Other [ edit ] Chali language , by ISO 639 code See also [ edit ] [REDACTED] Search for "tgf" on Misplaced Pages. All pages with titles beginning with TGF All pages with titles beginning with Tgf All pages with titles containing tgf Topics referred to by

84-509: A chloride concentration that is below a target value. A higher fluid flow rate in the TAL allows less time for dilution of the tubular fluid so that MD chloride concentration increases. Glomerular flow is decreased if the chloride concentration is above the target value. Constricting the smooth muscle cells in the afferent arteriole, results in a reduced concentration of chloride at the MD. TGF stabilizes

112-450: A decrease in the GFR (glomerular filtration rate), resulting in a decreased concentration of sodium and chloride ions in the filtrate and/or decreased filtrate flow rate. Reduced blood pressure means decreased venous pressure and, hence, a decreased peritubular capillary pressure. This results in a smaller capillary hydrostatic pressure , which causes an increased absorption of sodium ions into

140-530: A depressed GFR. Sodium chloride is sensed by the macula densa mainly by an apical Na-K-2Cl cotransporter (NKCC2). The relationship between the TGF and NKCC2 can be seen through the administration of loop diuretics like furosemide . Furosemide blocks NaCl reabsorption mediated by the NKCC2 at the ascending loop of henle, which leads to increased renin release. Excluding loop diuretic use, the usual situation that causes

168-451: A reduction in reabsorption of NaCl via the NKCC2 at the macula densa (DCT) is a low tubular lumen concentration of NaCl due to low GFR. Reduced NaCl uptake via the NKCC2 at the macula densa leads to increased renin release, which leads to restoration of plasma volume, and to dilation of the afferent arterioles, which leads to increased renal plasma flow and increased GFR. The macula densa's detection of elevated sodium chloride concentration in

196-591: A signal from the macula densa that has two effects: (1) it decreases resistance to blood flow in the afferent arterioles, which raises glomerular hydrostatic pressure and helps return the glomerular filtration rate (GFR) toward normal, and (2) it increases renin release from the juxtaglomerular cells of the afferent and efferent arterioles, which are the major storage sites for renin. As such, an increase in sodium chloride concentration would result in vasoconstriction of afferent arterioles, and reduced paracrine stimulation of juxtaglomerular cells. This demonstrates

224-488: Is a negative feedback loop in which the chloride ion concentration is sensed downstream in the nephron by the macula densa (MD) cells in the tubular wall near the end of TAL and the glomerulus. The muscle tension in the afferent arteriole is modified based on the difference between the sensed concentration and a target concentration. Vasodilation of the afferent arteriole, which results in increased glomerular filtration pressure and tubular fluid flow, occurs when MD cells detect

252-459: Is different from Wikidata All article disambiguation pages All disambiguation pages Tubuloglomerular feedback The kidney maintains the electrolyte 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 Fluid flow through

280-434: Is diluted because the cell's walls are water-impermeable and do not lose water as NaCl is actively reabsorbed. Thus, the TAL is an important segment of the TGF system, and its transport properties allow it to act as a key operator of the TGF system. A reduction of GFR occurs as a result of TGF when NaCl concentration at the sensor site is increased within the physiological range of approximately 10 to 60 mM. The TGF mechanism

308-405: Is usually limited in magnitude. A mediating agent is released or generated as a function of changes in luminal NaCl concentration. The size of the TGF response is directly dependent upon these changes. "In part because of the striking effect of deletion of A1 adenosine receptors (A1AR), adenosine generated from released ATP has been proposed as the critical TGF mediator. A modulating agent affects

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336-471: The vasa recta at the proximal tubule . Hence, a decrease in blood pressure results in less sodium chloride present at the distal tubule , where the macula densa is located. The macula densa senses this drop in salt concentration and responds through two mechanisms, both of which are mediated by prostaglandin release. First, prostaglandins preferentially vasodilate the renal afferent arteriole, decreasing afferent arteriole resistance and, thus, offsetting

364-500: The Na and Cl concentrations in early distal tubule fluid lower. The signal eliciting the TG feedback response is affected. The increased load on the kidney of high-protein diet is a result of an increase in reabsorption of NaCl . Factors that increase TGF sensitivity include: Macula densa In the kidney , the macula densa is an area of closely packed specialized cells lining

392-429: The TGF response without input regarding luminal NaCl. The agents are vasoactive substances that alter either the magnitude or the sensitivity of the TGF response. Factors that decrease TGF sensitivity include: The threshold at which the loop of Henle flow rate initiates feedback responses is affected. A high protein diet affects the feedback activity by making the single nephron glomerular filtration rate higher, and

420-507: The arterioles that will release renin if a fall in blood pressure (i.e. decreased stretch of arteriole due to less blood flow) in the arterioles is detected. Furthermore, JG cells contain beta-1 adrenergic receptors , and so activation of the sympathetic nervous system will further stimulate renin release. Thus, a drop in blood pressure results in preferential vasodilation of the afferent arterioles , increasing renal blood flow (RBF), renal plasma flow (RPF) and GFR due to greater blood flow to

448-408: The decrease in glomerular hydrostatic pressure caused by the drop in blood pressure. Second, prostaglandin activates prostaglandin-sensitive specialized smooth muscle cells of the renal afferent arterioles , juxtaglomerular cells (JG cells), to release renin into the bloodstream. The JG cells can also release renin independently of the macula densa. There are stretch-sensitive baroreceptors lining

476-407: 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. 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). As the TAL ascends through the renal cortex, it encounters its own glomerulus , bringing

504-439: The glomerulus. Note that there is no change in filtration fraction , as both GFR and RPF are increased. It also results in the release of renin, which, through the renin–angiotensin system , causes constriction of the efferent arterioles , which ultimately increases hydrostatic pressure in the glomerulus. The process triggered by the macula densa helps keep the GFR fairly steady in response to varying artery pressure. Damage to

532-484: The higher range of NaCl concentrations (2). When feedback regulation of afferent arteriolar tone is prevented by interrupting the feedback loop, and when the sensing mechanism is fully activated by saturating NaCl concentrations, TGF reduces GFR on average by approximately 45% and PGC by approximately 20%. Afferent arteriolar resistance increases by 50% or less, consistent with a radius reduction of approximately 10%, if Poiseuille's law holds. Thus, TGF-induced vasoconstriction

560-448: The macula densa feedback, where compensatory mechanisms act in order to return GFR to normal. The release of renin is an essential component of the renin–angiotensin–aldosterone system ( RAAS ), which regulates blood pressure and volume . The cells of the macula densa are taller and have more prominent nuclei than surrounding cells of the distal straight tubule (cortical thick ascending limb). The close proximity and prominence of

588-449: The macula densa to rest at the angle between the afferent and efferent arterioles . 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. The macula densa uses the composition of the tubular fluid as an indicator of GFR. A large sodium chloride concentration is indicative of an elevated GFR, while low sodium chloride concentration indicates

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616-416: The macula densa would impact blood flow to the kidneys because the afferent arterioles would not dilate in response to a decrease in filtrate osmolarity and pressure at the glomerulus would not be increased. As part of the body's blood pressure regulation, the macula densa monitors filtrate osmolarity; if it falls too far, the macula densa causes the efferent arterioles of the kidney to contract, thus increasing

644-445: 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. Tubuloglomerular feedback (TGF) regulates tubular flow by detecting and correcting changes in GFR. Active transepithelial transport is used by the thick ascending limb of loop of Henle (TAL) cells to pump NaCl to the surrounding interstitium from luminal fluid. The tubular fluid

672-439: The nuclei cause this segment of the distal tubule wall to appear darker in microscopic preparations, hence the name macula densa . Macula densa cells sense changes in sodium chloride level, and will trigger an autoregulatory response to increase or decrease reabsorption of ions and water to the blood (as needed) in order to alter blood volume and return blood pressure to normal. A decrease in afferent arteriole diameter causes

700-403: The same term [REDACTED] This disambiguation page lists articles associated with the title TGF . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=TGF&oldid=1156282782 " Category : Disambiguation pages Hidden categories: Short description

728-407: The trans-JGA signaling cascade is the glomerular afferent arteriole; its response consists of an increase in net vasoconstrictor tone resulting in reductions of glomerular capillary pressure (PGC) and glomerular plasma flow. Efferent arterioles appear to play a lesser role; experimental evidence supports both vasoconstriction and vasodilation, with perhaps the former in the lower range and the latter in

756-408: The tubular lumen, which leads to a decrease in GFR, is based on the concept of purinergic signaling . In response to increased flow of tubular fluid in the thick ascending limb/ increased sodium chloride (salt) concentration at the macula densa: In response to decreased flow of tubular fluid in the thick ascending limb / decreased salt concentration at the macula densa: The critical target of

784-437: The wall of the distal tubule where it touches the glomerulus . Specifically, the macula densa is found in the terminal portion of the distal straight tubule ( thick ascending limb of the loop of Henle ), after which the distal convoluted tubule begins. The cells of the macula densa are sensitive to the concentration of sodium chloride in the thick ascending loop of henle. A decrease in sodium chloride concentration initiates

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