Renal acid base balance Flashcards
How do we maintain renal pH?
*Matching excretion of acid-base equivalents to their input
*Regulating ratio of weak acids to their conjugate bases in buffer systems
What are the major buffers in the blood?
H2CO3 ⇄ H+ + HCO3−
HProt ⇄ H+ + Prot−
HHb ⇄ H+ + Hb−
What are the major buffer in interstitial fluid?
H2CO3 ⇄ H+ + HCO3−
What are the major buffer in intracellular fluid?
HProt ⇄ H+ + Prot−
H2PO4– ⇄ H+ + HPO4
How is the proximal tubule involved in acid base balance?
*Reabsorbs majority of filtered bicarbonate (normally about 80%)
*Produces and secretes ammonium
How is the thick ascending limb of henle’s loop involved in acid base balance?
Reabsorbs most of remaining filtered bicarbonate (normally about 10%–15%)
How is the distal nephron involved in acid base balance?
*Reabsorbs remaining filtered and secreted bicarbonate (type A intercalated cells)
*Acidifies tubular fluid (type A intercalated cells)
*Secretes bicarbonate (type B intercalated cells)
*Secretes ammonia and ammonium (type A and non-A, non-B intercalated cells)
What are the steps involved in proximal tubular reabsorption of bicarbonate?
- In the lumen filtered bicarbonate
combines with H+ to form CO2 and
water - CO2 diffuses into the cell
- In the tubular cell CO2 combines
with water to form H2CO3 - H2CO3 breaks into H+ which is
excreted with Na/H exchanger - HCO3 moves into interstitium
- Na is pumped into the interstitium
What are the steps involved in distal tubular H+ excretion?
*H+ generated from H2O and CO2
is actively pumped out in lumen
*H+ in the lumen combines with
HPO42-
What are the steps involved in distal tubular ammonia secretion?
- Ammonia is generated from
Glutamate - NH4+ breaks into H+ and NH3
- NH3 diffuses out into lumen
- NH3 combines with H+
- NH4+ is excreted in urine
