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Thursday, April 5, 2007

Effects of Aldosterone are High Yield for the USMLE

Scientists want to study the effect of that 1 mg of aldosterone will have on a healthy human volunteer. What changes can they predict in Na+ in grams, [Na+], pH, Urinary output, and K?

  • Na+ in grams increases
    • Aldosterone causes sodium (and water since water follows Na+) reabsorption in the principal cells of the distal convoluted tubule (DCT)
  • Concentration of Na+ stays the same
    • Since sodium is reabsorbed with water, the concentration will remain the same
  • pH will increase
    • Aldosterone causes H ion excretion in the intercalated cells of the DCT (via a Na/H-ATPase antiport pump)
  • Urinary output decreases
    • Since aldosterone causes the reabsorption of sodium and water from the DCT less remains in the urine that is forming
  • Potassium in grams will decrease in concentration and grams
    • Aldosterone is sodium sparring and potassium wasting (repeat this line to yourself 5 times)

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