Renal Acid-Base Regulation Flashcards
What is protein function highly sensitive to?
Hydrogen ions
What is acid-base management focused primarily on?
Hydrogen ions
Major blood buffer?
HCO3-
What is the primary acute regulator of pH?
Ventilation via the carbonic anhydrase reaction
What is the long-term regulator of pH?
The kidney
What is the ratio we are looking at?
HCO3-/CO2
What is the isohydric principle?
All buffer in a common solution are in equilibrium with the same H+ concentration
Effect of acidic plasma on ventilation?
Increase in ventilation
What does hypoventilation cause?
Primary respiratory acidosis
What does hyperventilation cause?
Primary respiratory alkalosis
What causes metabolic acidosis?
Ingestion, infusion or production of a fixed acid (acid source other than HCO3-)
What causes metabolic alkalosis?
A relative loss of fixed acids from the body
What occurs in compensatory changes?
The opposite value will increase in order to make the ratio of HCO3-/CO2 normal but not necessarily normal values for either
What are the major acid-base functions of the kidneys?
- ) To retrieve filtered and form new HCO3-
2. ) To retain and secrete the H+ filtered
Where is HCO3- reabsorbed in the nephron?
Proximal tubule (80%) Thick ascending limb (10%) Distal nephron (10%)
How is HCO3- reabsorbed?
First has to be broken down as CO2 and H20 absorbed through apical and resynthesized in the tubular cell and pumped out via Na/HCO3- pump
How is H+ secreted?
Inside tubular cells H2CO3 is broken down and H+ is pumped out while Na+ is pumped in (NHE)
Depletion of what stimulates NHE?
ANG-II
NE
Cortisol
K+
What do alpha-intercalated cells do?
Acidify urine
How do alpha-intercalated cells work?
Apical: H/K ATPase (excrete H+ and absorb K+)
Basolateral: pump out HCO3- and take in Cl- via
What effect does aldosterone have on alpha-intercalated cells?
Stimulated H+ secretion and HCO3 absorption
What does long period of aldosteronism cause?
K+ depletion
Increased H+ secretion (alkalosis)
What occurs when more H+ is filtered compared to HCO3-?
H+ is buffered by phosphate leading to an increased absorption of HCO3-
What provides the most important mechanism for generating new HCO3 during chronic acidosis?
Addition of NH4+ to the tubular fluid
What happens for each NH4+ excreted?
A new HCO3- is formed
What effect do glucocorticoids, A-II, Norepinephrine have on acid-base balance?
Stimulates Na-H exchanger in proximal tubule stimulating more H+ secretion
What affect do mineralocorticoids (such as aldosterone) have on acid-base balance?
Stimulates H+ secretion by increasing the apical H+-pump and the Cl-HCO3 exchanger, Na reabsorption in the collecting tubules and ducts and K+ depletion mechanism
What does chronic renal failure cause?
Metabolic acidosis
How does chronic renal failure cause acid-base conditions?
Reduced excretion of phosphates and NH4+
Reduces plasma HCO3-
