l12 acid base

Question 1

how many m moles of CO2 produced from metabolism

Answer 1

20,000 m moles

Question 2

what are volatile and non volatile acids

Answer 2

volatile acids are H2CO2 and CO2, fixed acids are nonvolatile acids (H+ A-)

Question 3

how many m moles of fixed acids are produced daily

Answer 3

60 m moles

Question 4

how much filtered HCO3 must be reabsorbed to maintain acid-base balance

Answer 4

4300 meq (24 meq/L X 180 L/day)

Question 5

how much HCO3- needs to be produced per day

Answer 5

60 meq

Question 6

what is the dominant H+ mechanism of transport in proximal and distal tubule?

Answer 6

• proximal: NHE3 in prosimal (depends on Na-K ATPase basolateral)
• distal/cd: H+ active pump on apical membrane, lowers pH of luminal fluid below proximal tubule

Question 7

draw bicarbonate reabsorption in proximal tubule

Answer 7

should have:

apical: co2 diffusing in, H+ moving out by Na/H exchanger or ATPase
basolateral: HCO3- moving out with Na and 3Na out:2K in

Question 8

what are the two urinary buffers of h+

Answer 8

phosphate (in luminal fluid) and ammonia (in proximal tubule cells, derived from metab of glutamine/amino acids)

Question 9

what is titratable acidity

Answer 9

all buffers in urine with pk around urine pH, most importantly phosphates NOT NH4

Question 10

how much of the urine acid is accounted for by titratable acids

Answer 10

1/3 of titratable acids account for urine acidity

Question 11

whend does endogenous production of filterable buffer/titratable acids increase?

Answer 11

in diabetes with production of ketoacids

Question 12

how is nh4 transported

Answer 12

in proximal tubule: via NH4/Na exchange into lumen
TAL: reabsorbed by substituting on Na/2Cl/K co transporter and is in equilibrium with NH3 in interstitium
cd: Rh glycoproteins transport NH3 and H into fluid where NH4 is trapped and maintains interstitial gradient

Question 13

what hormones and transporters are stimulated by acidosis

Answer 13

• ET1 transporter in pt cells increase NHE3 NBCe1 transporters
• cortisol from adrenal cortex increase NHE3 NBCe1 transporters
• PTH- inhibits phosphate reabsorption in PT so it can be used as T.A
• increase NHE3 Rh glycoproteins and H ATPAse in acute response
• increase proteins ammoniagenesis for chronic response

Question 14

Primary disturbance of respiratory acidosis, what is the effect on plasma k (hypo or hyper-kalemia)?

Answer 14

Respiratory disturbance won’t normally affect k, if anything H moves into cells and K moves out of cells and increases plasma K (hyperkalemia)

Question 15

Metabolic alkalosis has what effect on plasma K

Answer 15

Movement of H out of cells promotes K uptake into cells and causes hypolalemi

Question 16

Example of metabolic acidosis

Answer 16

Diarrhea causes loss of HCO3-from body and thus decrease in buffering.

Question 17

Calculate total H secreted

Answer 17

Total h = reabsorbed HCO3- + new HCO3-
reabsorbed HCO3- = filtered HCO3- - lost urine

NEW HCO3- secretes H into urine= TA + NH4+

Question 18

Diarrhea

• what is the composition of diarrhea fluid
• what is hr and bp
• hyper or hypo ventilating
• is hematocrit high or low
• what is plasma Na, Cl-, K, HCO3-, and Cre

Answer 18

Diarrhea fluid is isosmotic, alkaline (lots of HCO3-), high in K

• bp is low and hr is fast - sympathetics
• high hematocrit because losing fluid from ECF
• hyperventilating to breathe off CO2 to lowed pH
• diarrhea is metabolic acidosis with respiratory compensation
• plasma Na no change because losing isosmotic fluid, [Cl-] is high to balance loss of HCO3-, hypo kalemia (H in, K out, and K secreted due to high tubular flow), HCO3- low because loss
• Cre is high in plasma because GFR is low