Acid-Base Regulation by the Kidneys — Flashcards

Flashcard 1: PCT cells are involved in sustaining _____ which increases solute and water reabsorption in response to increased GFR.

Answer: glomerulotubular balance

Flashcard 2: As pH of the tubular fluid _____, the excretion of H+ as NH4+ increases

Answer: decreases

Flashcard 3: If the patient of diabetes mellitus (1 or 2) has type IV renal tubular acidosis, they will present with _____ excretion of ammonia in the urine

Answer: decreased

Flashcard 4: _____ (Type 1) renal tubular acidosis is due to a defect in the ability of alpha-intercalated cells to secrete H+

Answer: Distal

Flashcard 5: HCO3- is transported across the basolateral membrane into the blood by:\n1. Proximal tubule: _____\n2. Alpha-intercalated cells: Cl--HCO3- exchange

Answer: Na+-HCO3- cotransport

Flashcard 6: Carbonic Anhydrase _____ is present on the inside of the PCT tubular cell

Answer: II

Flashcard 7: _____ renal tubular acidosis is also known as type 4 RTA

Answer: Hyperkalemic

Flashcard 8: Carbonic Anhydrase _____ is present on the luminal side of the PCT tubular cell

Answer: IV

Flashcard 9: 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 10: 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).