Potassium Regulation — Flashcards

Flashcard 1: The _____ cells of the late distal tubule and collecting duct secrete H+

Answer: alpha-intercalated

Flashcard 2: Some _____ in the cells of the thick ascending limb diffuse back into the lumen, creating a lumen positive potential difference

Answer: K+

Flashcard 3: In the presence of _____, aquaporin 2 channels are inserted in the luminal membrane of principal cells of the late distal tubule and collecting duct

Answer: ADH

Flashcard 4: The major solutes absorbed in the proximal tubule are _____ and NaHCO3

Answer: NaCl

Flashcard 5: Reabsorption of Na+ in the collecting duct creates a _____ luminal potential that facilitates K+ excretion

Answer: negative

Flashcard 6: Mineralocorticoids (aldosterone) cause increased renal _____ secretion via action on the alpha-intercalated cells of the late distal tubule and collecting duct

Answer: H+

Flashcard 7: The _____ cells of the late distal tubule and collecting duct secrete K+

Answer: principal

Flashcard 8: What is the formula for renal clearance ($C_x$)?

Answer: $C_x = \frac{U_x V}{P_x}$

Extra: $U_x$ = Urine concentration of X $P_x$ = Plasma concentration of X $V$ = Urine flow rate

Flashcard 9: What equation is used to calculate **free-water clearance** ($C_{H_2O}$)?

Answer: $$C_{H_2O} = V - C_{osm}$$ (where $V$ = urine flow rate; $C_{osm}$ = osmolar clearance)

Extra: Free-water clearance ($C_{H_2O}$) represents the volume of solute-free water that must be added to or removed from the urine to make it isotonic with plasma. - If **$C_{H_2O} = 0$**: Urine is isosthenuric (isosmotic to plasma). - If **$C_{H_2O} > 0$**: Free water is excreted (dilute urine; $U_{osm} < P_{osm}$). Seen in low ADH states (e.g., diabetes insipidus, water intoxication). - If **$C_{H_2O} < 0$**: Free water is reabsorbed (concentrated urine; $U_{osm} > P_{osm}$). Seen in high ADH states (e.g., SIADH, dehydration).

Flashcard 10: The fraction of filtered water reabsorbed may be measured using the equation: _____

Answer: 1 − 1 / (TF/P)inulin