5/6: Acid-base regulation by the kidney - Wilson Flashcards
state the HH equation
look at notes
describe respiratory acidosis
hypoventilation
increased PCO2
pH less than 7.4
describe respirtaory alkalosis
hyperventialation
decreased PCO2
pH above 7.4
describe metabolic acidosis
loss of HCO3-
ph less than 7.4
describe metabolic alkalosis
increase in HCO3- concentartion
pH greater than 7.4
kidneys regulate H+ ________ and HCO3- _______
excretion
reabsorption
H+ ions are removed by
binding to filtered buffers (H2PO4) or bidning to NH3
elimination of HCO3- in urine is equivalent to..
adding H+ to body
insertion of ATPase into luminal membrane of distal tubule is stimulated by…
low pH
high pH stimulates recycling of ATPase back to the cytoplasm
there is distal and proximal acidification – proximal uses gradient
distal uses ATPase to directly pump out H+
where is bicarbonate reabsorbed?
nearly all is filtered but reabsorbed in proximal tubule (90%) and collecting duct (10%)
true or false: reabsorption of HCO3- back from tubular lumen into filtrate is by simple transport
FALSE
H+ secreted into tubular lumen reacts with HCO3- in the filtrate to form carbonic acid
carbonic acid is converted to H20 and CO2 by carbonic anhydrase
H2O and CO2 diffuse back into renal tubular cell where they are formed back into carbonic acid by carbonic anhydrase
H+ is then secreted into tubular lumen and HCO3- is exported to blood with sodium
NET: movement of NaHCO3 from filtrate to blood
action of B type intercalated cells of collecting tubule
polarity of membrane transporters can be reverese — can acitively secrete bicarbonate and reabsorb proton if needed (important in metabolic alkalosis)
limiting urine pH
4.4.
why? H+ translocating ATPase now inhibited
ability to excrete H+ as H2PO4 is limited by
- amount of HPO42- in filtrate
- requirement of body to retain phosphate
for each newly-formed H2PO4- excreted in urine…
one H+ eliminated
one new HCO3- formed and added to blood
measure of H+ excreted in urine as undissociated weak acid
titratable acid
how is H+ excreted as NH4+
glutaminase converts glutamine to glutamate
glutamate converted to alpha-ketoglutarate and NH4+ by glutamate dehydrogenase (yields two HCO3- )
NET: excretion of protons into lumen and new molecules of HCO3- to blood
normal ???
arterial PCO2 arterial pH arterial bicarb urinary titratable acid urinary ammonium ion
40 torr pH 7.35-7.45 24 mmol/L *** this is a calculated value 0-20 mmol/day 20-40 mEq/day
normal anion gap
8-12 mEq-L
equation for anion gap
sodium - (bicarb and chloride)
metabolic acidosis produces ______ anion gap
large
there is so unmeasured anion
difference between measure bicarb and bicard predicted by normal buffer slope at that pH
base deficit
what happens to bicarb levels with acute respiratory acidosis?
slightly increased
compensated chronic respiratory acidosis has a greater increase in bicarb
what is hyperchloremic/non-gap metabolic acidosis?
as bicarb goes down, chloride goes up so there is no anion gap
- occurs with gastrointestinal or renal loss o fHCO3-
