Loop diuretics acts on?
ANSWER: (B) Ascending limbREF: Goodman Gillman pharmacology 11th ed page 482See APPENDIX-14 below for "RENAL PHYSIOLOGY"Loop diuretics inhibit the activity of the Na+-- K+--2C1- symporter in the TAL (thick ascending limb) of the loop of Henle, hence, their designation as loop diuretics.DIURETICSITE OF ACTIONMECHANISM OF ACTIONCarbonic anhy- drase inhibitorsProximal convovulted tubules* Inhibit both the membrane-bound and cytoplasmic forms of carbonic anhy- draseLoop diureticsAscending limb of loop of henle* Na-K-2C1 Transporter inhibitor* Weak carbonic anhydrase inhibitor* Redistribution of renal blood flowEthacrinic acidAscending limb of loop of henle* Na-K-2C1 Transporter inhibitorThiazideEarly distal tubule* Na-Ci symporter inhibitorSpirinolactoneInterstitial side of distal tubule or collecting duct* Binds to intracellular mineralocorticoid receptorTriamterene and amiliorideLuminal side of distal tubule or collecting duct* Blocks luminal Na channels APPENDIX - 14 Renal 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 {minor}reabsorption (65%, isosmotic)reabsorption (25%o, thick ascending, Na-K-2C1 symporter)reabsorption (5%, sodium- chloride symporter)reabsorption (5%, principal cells),stimulated byaldosterone via ENaCChlorideUsually follows sodium. Active (transcellular) and passive (paracellular)reabsorptionreabsorption (thin ascending, thick ascending,Na-K-2C1symporter)reabsorption(sodium-chloridesymporter) WaterUses aquaporin water channels. See also diuretic.absorbed osmotically along w'ith solutesreabsorption(descending) reabsorption (regulated by ADH, via arginine vasopressin receptor 2)BicarbonateHelps maintain acid- base balance.Reabsorption (80-90%)reabsorption(thickascending) reabsorption (intercalated cells, via band 3 and pendrin)ProtonsUses vacuolar H+ATPase secretion(intercalatedcells)PotassiumVaries upon dietary needs.Reabsorption (65%)reabsorption (20%, thick ascending, Na-K-2C1 symporter) secretion (common, via Na+/K+- ATPase, increased by aldosterone), or reabsorption (rare, hydrogen potassium ATPase)CalciumUses 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.reabsorptionreabsorption(thickascending)reabsorption PhosphateExcreted as titratable acid.Reabsorption (85%) via sodium/phosphate cotransporter. Inhibited by parathyroid hormone. Carboxylate Reabsorption (100%) via carboxylate transporters.
Descending limb
Thick ascending limb
Cortical segment
Collecting duct
Diuretic