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20 Cards in this Set
- Front
- Back
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What is the main transporter that provides gradients for passive transporters in the renal tubule?
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Na+/K+-ATPase in the basolateral membrane
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What do loop diuretics specifically inhibit?
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Na+/K+/2Cl cotransport in the thick ascending LOH
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Is fluid leaving the thick ascending limb isotonic, hypotonic or hypertonic & why?
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Hypotonic - thick ascending limb is impermeable to water, so filtrate is diluted as ions are reabsorbed
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What is tubular counter-current multiplication?
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A concentration gradient is actively generated where small horizontal differences in solute concentration between tubular fluid & interstitium are multiplied vertically
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What do thiazide diuretics do?
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inhibit Na+/Cl- cotransport in the distal tubule
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What does amiloride do?
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inhibit sodium channels in the collecting duct to stop sodium reabsorption
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What is the action of aldosterone on the kidney?
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stimulates collecting duct epithelial sodium channels
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Outline 3 problems with medications in renal failure?
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- failure to excrete a drug or its metabolites
- poorly tolerated side-effects (increased K+) - some drugs less effective with reduced renal function e.g. diuretics Dialysis may lead to loss of therapeutic effect |
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How does urine pH affect medication?
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- speed of drug excretion
- ionisation - acidic drugs more readily ionised in alkaline urine & vice versa. ionised substances easier to excrete. |
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What is the overall effect of diuretics?
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increase excretion of Na+ (& usually Cl-) with secondary water loss due to natriuresis
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What are the 2 pharmacodynamic actions of diuretics?
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- act directly on nephron cells (most diuretics)
- indirectly exert effects by modifying filtrate content (osmotic diuretics) |
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define diuresis
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the formation of urine by the kidneys
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define diuretic
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substance that promotes the excretion of urine
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define natriuresis
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renal excretion of sodium
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define natriuretic
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substance that promotes renal excretion of sodium
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List 3 consequences of fluid overload
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-oedema
-congestive heart failure -hypertension |
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Name the 3 most commonly used diuretic classes
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- loop diuretics
- thiazides - potassium-sparing diuretics (aldosterone antagonists) (rarely used: carbonic anhydrase inhibitors, osmotic diuretics, specialised ADH antagonists) |
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What is the role of carbonic anhydrase?
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catalyses the interconversion of CO2 & H2O to bicarbonate & protons (H+) or vice versa
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What does acetazolamide do?
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inhibits carbonic anhydrase
- block HCO3- absorption - block Na+ reabsorption - prevent exchange & secretion of H+ increases excretion of bicarbonate with accompanying Na+, K+ & water increased flow of an alkaline urine & metabolic acidosis |
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what is acetazolamide used for?
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carbonic anhydrase inhibitor - promotes HCO3- secretion
Not normally used as kidney diuretic Used to - reduce intraocular pressure - mountain sickness - alkalosis correction |
