Renal Transport Of HCO3- And H+ And Acid-Base Disorders

5/4/10 9 Am
Created May 6, 2010
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Side ASide B
What is the normal pattern of acid-base balance?
CO2 + nonvolatile acids are the acids you haveHCO3 - is the baseCO2 is blown off by the lungs,...
What are the 3 systems that control plasma pH?
1. Lungs2. Kidneys3. Buffers
What is the role of a proton buffer?
To minimize changes in pH
What is the equation for acid dissociation/formation?
HA <----> H+ + A-
What is the equation for pH?
pH = - log [H+]
WHat is the equation for pK?
pK = - log [K]
What is the Henderson-Hasslebach equation?
pH = pKa + log ([A-])/[HA]
What is the most important buffer in the body?
serum bicarbonate
What are the 2 roles of the kidneys in acid-base balance?
1.  Secrete H+ to reabsorb almost all of the filtered HCO3-2.  Secrete daily net...
Net urinary acid excretion has 2 parts.  What are they?
1. H+ excretion requires binding of H+ to buffers (ex: phosphate, creatinine, urea) to produce...
What is the equation for net urinary acid excretion?
Net urinary acid excretion = titratable acids + ammonium - (excretion of filtered HCO3-)
Why does the excretion of filtered HCO3- have to be subtracted from acid excretion to get the...
Because the reabsorption of HCO3- requires the secretion of H+.  So if some of the HCO3-...
How is an acid challenge handled?
3 steps are involved:1. HCO3- and non-HCO3- buffers in the plasma neutralize most of the H+B-...
HCO3- reabsorption requires __________
H+ secretion (NOT excretion!)
Describe HCO3- reabsorption.
HCO3- is converted by a luminal membrane CA to CO2 + OH-, and secreted H+ combines with the...
Describe excretion as a titratable acid.
For every H+ that is secreted, a new HCO3- is produced (by the intracellular carbonic anhydrase)...
Where is NH4+ secreted in the nephron?
Proximal tubule
Where is NH4+ reabsorbed in the nephron?
Describe NH4+ reabsorption by the TAL.
Apical membrane = NH4+ channels, Na/2Cl/NH4 cotransporterNH4 is broken down into H+ and NH3...
Describe NH4+ recycling in the LoH.
NH4+ reabsorbed by the TAL is broken down into NH3 and H+ in the interstitium.1) NH3 diffuses...
Describe the role of urea and glutamine metabolism in acid/bases.
Proteins and amino acid breakdown produces nitrogenous waste, which has to be converted to...
What are the effects of respiratory acidosis on H+ secretion?
Respiratory acidosis (i.e. increased PCO2) increases H+ secretion by an unknown mechanism
What are the effects of metabolic acidosis on H+ secretion?
Metabolic acidosis increases H+ secretion by increasing HCO3- uptake and reducing HCO3- backleak.
What are the effects of chronic metabolic acidosis on H+ secretion?
stimulates H+ secretion by increasing the activities of transporters and NH3 synthesis.
Name the 5 factors that increase HCO3- reabsorption
1. Respiratory acidosis (increased PCO2)2. Metabolic acidosis (decreased HCO3-)3. Hypokalemia 4....
Why does hypokalemia increase HCO3- reabsorption?
H/K pump on the a-intercalated cell, which is responsible for increasing K+ reabsorption.  Pumps...

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