4.4 Phys: Renal handling H+ and HCO3

Question 1

An increase or decrease in 1 pH unit correlates with what change in H+ concentration

Answer 1

1pH= x10 H+ concentration

Question 2

An increase or decrease in 0.3pH unit correlates with what change in H+

Answer 2

0.3pH=x2 H+ concentration

Question 3

Temperature and pH

Answer 3

Increase in temp–>Decrease in pH

Decrease in temp–>Increase in pH

Question 4

3 mechanisms that contribute to maintaining pH in normal range?

Answer 4

1. Buffering H+ in both ECF and ICF
2. Respiratory compensation
3. Renal compensation

Question 5

In DM type 1, what happens when no insulin is given.

Answer 5

1.Decrease glucose uptake.
2. Increased protein catabolism–>Increase AA levels, glucogenic substrate
3. Increase lipolysis, resulting in increased blood levels of free fatty acids
4. Increased hepatic ketogenesis from fatty acid substrad
Fixed acids: B-hydroxybutryic acid and acetoacetic acid, due to incomplete oxidation of carbogydrate and fat

Question 6

Fixed acids that can be ingested (4) and lead to metabolic acidosis.

Answer 6

Aspirin, Oxyalic acid from green veggies, glycolic acid from ethylene glycol, and methanol or wood alcohol

Question 7

Explain the mechanism of Methanol to cause metabolic acidosis

Answer 7

Methanol–>(Alcohol dehydrogenase)Formaldehyde–>(Formaldehyde dehydrogenase) Formic acid–>Metabolic acidosis and injury

Question 8

ICF buffer and ECF buffer

Answer 8

ICF: HgB
ECF: HCO3

Question 9

Albumin as buffer

Answer 9

Albumin can buffer H+ because it has binding spots for H+ and Ca+

Question 10

What happens to Ca+ when there is increased pH

Answer 10

Alkalemia–>Decreased Concentration of Ca+ because more spots to bind to albumin since there is low H+

Question 11

Calculation for net urinary acid excretion

Answer 11

Net urinary acid excretion= excreted H+bound to phosphate, creatine, uric acid+Excreted NH4-Excreted HCO3-

Question 12

Effect of ang II on acid base balance

Answer 12

Increase in Ang II acts on prox. tubule at the Na+/H+ antiporter. There is an increase H+ secretion resulting in more HCO3- reabsorption

Question 13

Uses for acetazolamide

Answer 13

Altitude sickness due to alkalosis–>Brings pH down by acidosis

Question 14

MOA of acetazolamide

Answer 14

Carbonic anhydrase inhibitor outside prox tubule–>limits HCO3 diuresis and decreases total body HCO3-

Question 15

effect of ECF volume expansion on HCO3 reabsorption

Answer 15

ECF vol expansion–>Decrease in HCO reabsorption because there is an increase in capillary pressure and decrease capillary oncotic pressure

Question 16

Effect of ECF volume contraction on HCO3

Answer 16

ECF volume contraction–>RAA activated–>Ang II increased–> increased H+secretion–>Increase HCO3- reabsorption–> Contraction alkalosis

Question 17

Contraction alkalosis examples (1 of 3): Loop diuretic

Answer 17

Loop Diuretics: Block Na/K/2Cl- cotransporter–>Hypokalemic–>alkalotic

Question 18

Contraction alkalosis examples (1 of 3): Thiazide Diuretic

Answer 18

Thiazide diuretics: Blocks NaCl cotransporter–> Increase Na+ and water excretion–>decrease ECF water vol–>Increase aldosterone at alpha intercalated–>Increase HCO3 reabsorbed

Question 19

Contraction alkalosis examples (1 of 3): Vomiting

Answer 19

Vomiting
Parietal cells make H+ and HCO3- from CO2 and water–>H+secreted in lumen of stomach–>HCO3- enters blood–>Vomit excretes H+ and HCO3- remains in blood and cannot be excreted

Question 20

Effect of Plasma CO2

Answer 20

CO2+H2O–>H+HCO3–>HCO3 is reabsorbed. H+ is secreted in the prox tubule

Question 21

Excretion of H+ as Titratable acid, H2PO4-

Answer 21

Alpha intercalated cell: Secreted H+ binds to HPO4 and excreted–> New HCO3- is reabsorbed

Aldosterone increases Na+ reabsorption and alpha intercalated cell

Question 22

What is minimum urine pH

Answer 22

4.4

Question 23

Excretion of NH4+ at proximal tubule and Alpha intercalated cell

Answer 23

Diffusion Trapping
Glutamine is diffused into prox tubule–>broken down into NH4+and HCO3—>NH3 diffuses into lumen acts as buffer for H+ excretion–>HCO3 is reabsorbed

In alpha intercalated cell: NH3 from medullary interstitiium from blood enters lumen at intercalated cell–>H+ secreted binds to NH3 and excreted as NH4+

Question 24

Where can NH4+ be reabsorbed

Answer 24

NH4+ can be reabsorbed in the TAL at Na/NH4+/2Cl-

Question 25

K+ and NH3 synthesis

Answer 25

Hyperkalemia inhibits NH3 synthesis and reduces the ability to excrete H+ as NH4+ causing Type 4 Renal tubular acidosis

Hypokalemia stimulates NH3 synthesis and increases ability to excrete H+ from NH4

Increase K+–>low H+excretion because Alkalotic

Decrease in K+–>Increase NH3–>Increase H+excretion as NH4–>Acidosis

Question 26

K+ concentration and acid base balance relationships

Answer 26

Hypokalemia–>alkalemia

Hyperkalemia–>Acidemia

Question 27

What 3 hormones can help balance K+ in cell

Answer 27

Epi, insulin and aldosterone