First Aid - Renal Physiology II Flashcards
Site of action of Angiotensin II in proximal convoluted tubule and what three compounds/ions are most affected?
Angiotensin II stimulates Na+/H+ exchange on lumenal border. This increases reabsorption of water and Na+ from the lumen and HCO3 from the cell (by decreasing intracellular H+).
What occurs in the thin descending loop of Henle?
Passive reabsorption of H2O via medullary hypertonicity. Impermeable to Na+. Concentrating segment, makes urine hypertonic.
What occurs in the thick ascending loop of Henle?
Active reabsorption of Na+, K+, Cl-. Na/K/ATPase pump on basolateral face actively pumps Na+ out of cells, Na+ gradient drives absorption of Na/K/Cl from lumen. K+ moves down gradient to lumen or interstitium. Cl moves to interstitium. Mg and Ca move through paracellular path by (+) charge created by K+ flow into lumen. Impermeable to H2O, makes urine less concentrated.
Where do Loop diuretics act (location in tubule and specific target)?
Loop diuretics act on the Na+/K+/Cl- co-transporters in the Thick ascending loop of Henle.
What occurs in the distal convoluted tubule?
Active reabsorption of Na+/Cl-, Ca2+ reabsorption, makes urine hypotonic. Na/K/ATPase pumps on basal aspect create Na+ gradient from lumen to cell, driving Na+ Cl- absorption.
What actions does PTH have and where does it act?
PTH inhibits Na/PO4 cotransporters in proximal tubule, increases PO4 excretion. PTH increases Na+/Ca2+ exchange on basal aspect DCT cells, increases Ca2+ reabsorption.
What occurs in the collecting tubule?
Reabsorption of Na+, secretion of K+ and H+, regulated by Aldosterone. Final location of Na+ reabsorption, most hormonal control of Na+/H2O reabsorption occurs here.
Where does aldosterone and aldosterone antagonists act?
In the collecting tubule/duct. Aldosterone acts on mineralocorticoid receptors, increasing Na+ channels on lumenal aspect. Aldosterone antagonists (amiloride, triamterene) block those Na+ channels.
Where does ADH act and what does it do?
ADH acts on the V2 receptors on Principle cells of the collecting duct, triggers insertion of aquaporins contained in vesicles on the lumenal surface. Increases water flow.
What is Fanconi syndrome?
Fanconi disease occurs in the Proximal Convoluted Tubule and is associated with increased excretion of AA, glucose, HCO3, PO4. May result in metabolic acidosis. Caused by hereditary defects (Wilson disease), ischemia, or nephrotoxins/drugs.
What is Bartter syndrome?
Bartter syndrome is a reabsorption defect in the thick ascending loop of Henle. Autosomal Recessive, affects Na/K/Cl co-transporter. Results in hypokalemia and metabolic alkalosis with hypercalciuria.
What is Gitelman syndrome?
Gitelman syndrome is a defect of NaCl cotransporters in the DCT. Leads to hypokalemia and metabolic alkalosis (like Bartter syndrome) but without hypercalciuria.
What is Liddle syndrome?
Liddle syndrome is autosomal dominant and causes increased Na+ reabsorption in the distal and collecting tubules (increased activity of Na+ channels). Results in hypertension, hypokalemia, metabolic alkalosis, and decreased aldosterone.
Mnemonic for the order of renal tubular defects by their location?
The kidneys put out FABulous Glittering Liquid. FAnconi - PCT; Bartter - Thick ascending loop of Henle; Gitelman - DCT; Liddle - Collecting tubule.
