Renal sodium reabsorption - wikipedia Renal sodium reabsorption Renal reabsorption of sodium ( Na ) is a part of renal physiology. It uses Na - H antiport, Na - glucose symport, sodium ion channels ( minor ). It is stimulated by angiotensin II and aldosterone, and inhibited by atrial natriuretic peptide. It is very efficient, since more than 25,000 m moles / day of sodium is filtered into the nephron, but only ~ 100 m moles / day, or less than 0.4 % remains in the final urine. Contents 1 Proximal tubule 2 Loop of Henle 3 Distal tubule 4 Collecting duct 4.1 Regulation 5 Overview table 6 References Proximal tubule Most of the reabsorption ( 65 % ) occurs in the proximal tubule. In the latter part it is favoured by an electrochemical driving force, but initially it needs the cotransporter SGLT and the Na - H antiporter. Sodium passes along an electrochemical gradient ( passive transport ) from the lumen into the tubular cell, together with water and chloride which also diffuse passively. Water is reabsorbed to the same degree, resulting in the concentration in the end of the proximal tubule being the same as in the beginning. In other words, the reabsorption in the proximal tubule is isosmotic. Loop of Henle Sodium is reabsorbed in the thick ascending limb of loop of Henle, by Na - K - 2Cl symporter and Na - H antiporter. It goes against its chemical driving force, but the high electrical driving force renders the overall electrochemical driving force positive anyway, availing some sodium to diffuse passively either the transcellular or paracellular way... Distal tubule In the distal convoluted tubule sodium is transported against an electrochemical gradient by sodium - chloride symporters. Collecting duct The principal cells are the sodium - transporting cells in the collecting duct system. Regulation Although only a fragment of total reabsorption happens here, it is the main part of intervention. This is e.g. done by endogenous production of aldosterone, increasing reabsorption. Since the normal excretion rate of sodium is ~ 100mmoles / day, then a regulation of the absorption of still more than 1000 mmoles / day entering the collecting duct system has a substantial influence of the total sodium excreted. Overview table Characteristics of Na reabsorption Characteristic proximal tubule loop of Henle Distal convoluted tubule Collecting duct system S1 S2 S3 descending limb thin ascending limb thick ascending limb connecting tubule initial collecting tubule cortical collecting ducts medullary collecting ducts reabsorption ( % ) 67 % 25 % 5 % 3 % reabsorption ( m moles / day ) ~ 17,000 ~ 6,400 ~ 1,300 ~ 700 Concentration ( m M ) 142 142 100 70 40 electrical driving force ( m V ) - 3 + 3 + 15 - 5 to + 5 - 40 chemical driving force ( m V ) 0 0 - 9 - 19 - 34 electrochemical driving force ( m V ) - 3 + 3 + 6 - 24 to - 14 - 74 apical transport proteins SGLT, Na - H antiporter ( passively ) Na - K - 2Cl symporter ( Na - H antiporter and passively ) sodium - chloride symporter ENaC basolateral transport proteins Na / K - ATPase Other reabsorption features isosmotic by principal cells, stimulated by aldosterone References Jump up ^ VI. Mechanisms of Salt & Water Reabsorption Archived 2007 - 02 - 10 at the Wayback Machine. ^ Jump up to : Walter F., PhD. Boron. Medical Physiology : A Cellular And Molecular Approaoch. Elsevier / Saunders. ISBN 1 - 4160 - 2328 - 3. Page 776 ^ Jump up to : Walter F., PhD. Boron. Medical Physiology : A Cellular And Molecular Approaoch. Elsevier / Saunders. ISBN 1 - 4160 - 2328 - 3. Page 777 ^ Jump up to : Walter F., PhD. Boron. Medical Physiology : A Cellular And Molecular Approaoch. Elsevier / Saunders. ISBN 1 - 4160 - 2328 - 3. Page 778 Physiology of the kidneys and acid - base physiology Renal function Secretion clearance Pharmacokinetics Clearance of medications Urine flow rate Reabsorption Solvent drag sodium chloride urea glucose oligopeptides protein Renal function Glomerular filtration rate Creatinine clearance Renal clearance ratio Urea reduction ratio Kt / V Standardized Kt / V Measures of dialysis Hemodialysis product PAH clearance ( Effective renal plasma flow Extraction ratio ) Filtration Renal blood flow Ultrafiltration Countercurrent exchange Filtration fraction Hormones Antidiuretic hormone Aldosterone Atrial natriuretic peptide Renin Erythropoietin Calcitriol Prostaglandins Acid - base balance Fluid balance Darrow Yannet diagram Body water : Intracellular fluid / Cytosol Extracellular fluid ( Interstitial fluid Plasma Transcellular fluid ) Base excess Davenport diagram Anion gap Arterial blood gas Winters ' formula Buffering Bicarbonate buffer system Respiratory compensation Renal compensation Other Fractional sodium excretion BUN - to - creatinine ratio Tubuloglomerular feedback Natriuresis Urine Retrieved from `` https://en.wikipedia.org/w/index.php?title=Renal_sodium_reabsorption&oldid=836410758 '' Categories : Renal physiology Hidden categories : Webarchive template wayback links Talk Contents About Wikipedia Add links This page was last edited on 14 April 2018, at 17 : 07. 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Question: where does most reabsorption in the renal tubule occur
Answer: in the proximal tubule