<prompt> In proximal convoluted tubule H is exchanged for?KNaHCO3--Cl--  <response>: ANSWER: B NaREF: Guyton physiology 11th ed page 55See APPENDIX-14 below for RENAL PHYSIOLOGYSodium-hydrogen counter-transport occurs in several tissues. An especially important example is in the proximal tubules of the kidneys, where sodium ions move from the lumen of the tubule to the interior of the tubular cell, while hydrogen ions are counter transported into the tubule lumen. APPENDIX - 14Renal Physiology:SubstanceDescriptionProximal TubuleLoop of HenleDistal TubuleCollectingDuctGlucoseIf glucose is not reabsorbed by the kidney, it appears in the urine, in a condition known as glucosuria. This is associated with diabetes mellitus.Reabsorption almost 100 via sodium- glucose transport proteins apical and GLUT basolateral. Oligopeptides, proteins, and amino acidsAll are reabsorbed nearly completely.reabsorption UreaRegulation of osmolality. Varies with ADHreabsorption 50 via passive transportsecretion reabsorption in medullary collecting ductsSodiumUses Na-H antiport, Na-glucose symport. sodium ion channels minorreabsorption 65, isosmoticreabsorption 25o, thick ascending, Na-K-2C1 symporterreabsorption 5, sodium- chloride symporterreabsorption 5, principal cells,stimulated byaldosterone via ENaCChlorideUsually follows sodium. Active transcellular and passive paracellularreabsorptionreabsorption thin ascending, thick ascending,Na-K-2C1symporterreabsorptionsodium-chloridesymporter WaterUses aquaporin water channels. See also diuretic.absorbed osmotically along with solutesreabsorptiondescending reabsorption regulated by ADH, via arginine vasopressin receptor 2BicarbonateHelps maintain acid- base balance.Reabsorption 80-90reabsorptionthickascending reabsorption intercalated cells, via band 3 and pendrinProtonsUses vacuolar HATPase secretionintercalatedcellsPotassiumVaries upon dietary needs.Reabsorption 65reabsorption 20, thick ascending, Na-K-2C1 symporter secretion common, via NaK- ATPase, increased by aldosterone, or reabsorption rare, hydrogen potassium ATPaseCalciumUses calcium ATPase,sodium-calciumexchangerreabsorptionreabsorption thick ascending via passive transport MagnesiumCalcium and magnesium compete, and an excess of one can lead to excretion of the other.reabsorptionreabsorptionthickascendingreabsorption PhosphateExcreted as titratable acid.Reabsorption 85 via sodiumphosphate cotransporter. Inhibited by parathyroid hormone. Carboxylate Reabsorption 100 via carboxylate transporters. 