Gene models + nephron function (3) Flashcards
Semester 1 year 1
What 2 types of cell are the late distal tubule and cortical collecting duct made up of?
-principal
-intercalated
What are the principal cells involved in?
-Na+ and H2O absorption
-K+ and H+ secretion
What are the 2 types of intercalated cell?
-alpha intercalated cell
-beta intercalated cell
What do the alpha and beta intercalated cells do?
-alpha - H+ secretion and HCO3- reabsorption
-beta - H+ reabsorption + HCO3- secretion
How does transport occur across the principal cell?
-Na+ moves out + K+ in via ATPase on basolateral membrane
-Na+ moves in via ENaC protein on apical membrane
-K+ moves out via ROML on apical membrane (stays in urine) + via Kir2.3 on basolateral membrane
-H2O moves in via aquaporin 2 on apical membrane + out via aquaporins 3 + 4 on basolateral membrane
What diuretic works on cells in the late distal tube + CCD and how?
-amiloride
-blocks ENaC to prevent sodium reabsorption, inhibiting water reabsorption
-excrete more sodium + water, decreasing blood volume
-treatment for high blood pressure
What are diseases that affect the principal cells of the late distal tubule and CCD?
-diabetes insipidus
-Liddle’s syndrome
What is diabetes insipidus?
When you struggle to concentrate the urine
Describe Liddle’s syndrome
-affects ENaC inheritance
-dominant inheritance
-retain too much sodium, so reabsorb more water, leading to hypertension
-hypokalaemia
Where do mutations occur to cause Liddle’s syndrome?
-in COOH tail of beta or gamma subunits
-deletes proline rich motifs
What does excessive sodium transport as a result of Liddle’s syndrome do to water reabsorption?
-more ENaC channels causes more sodium transport
-driving force for water reabsorption increased
-expansion of extracellular fluid volume + cardiac output
-mean arterial pressure = cardiac output x heart rate
What does excessive sodium transport as a result of Liddle’s syndrome do to potassium secretion ?
-more ENaC channels causes more sodium transport
-driving force for potassium secretion increased
-lose potassium in urine - hypokalaemia
What is treatment for Liddle’s syndrome?
-amiloride
-inhibitor of ENaC
How does transport across alpha intercalated cells work?
-H+ pumped across apical membrane using proton ATPase + is lost in urine
-AE1 protein on basolateral membrane - HCO3^- out + Cl- in
-bicarbonate made in cell absorbed using AE1 + chloride enters cell
-Cl- recycled out of cell using Cl- protein
How does transport across beta intercalated cells work?
-AE1 on apical membrane, Cl- transporter + proton ATPase on basolateral membrane
-Cl- moves into cell to allow HCO3^- to be secreted from cell + lost in urine
-net reabsorption of Cl-
-removal of H+ by proton ATPase into interstitial fluid then peritubular capillaries
