Regulation Of A-B Balance

Front 1

(Ab)normal blood pH values

Back 1

Normal: 7.4

Acidemia: < 7.35

Alkalemia: > 7.45

Front 2

Respiratory vs. Metabolic Acidosis

Back 2

Respiratory: abnormal PCO2

Metabolic: abnormal HCO3-

Front 3

H2CO3 as a buffer

Back 3

H2CO3 <=> H+ + HCO3- pK = 2.6

Buffering at physiological pH enabled by

- dissociation H2CO3 -> CO2 + H2O =>

CO2 + H2O <=> H+ + HCO3- pK = 6.1

- open system: once formed, CO2 can leave => the more buffer, the more power => ↑ pK

Front 4

Isohydric principle

Back 4

All buffers in a compartment are in equilibrium

-> overall A-B status can be inferred from measurement on just 1 buffer

CO2 can cross membranes freely => ECF ~ ICF pH

Front 5

Intracellular buffers

Back 5

HCO3-: ICF < ECF

Pi

Front 6

Imidazole alphastat hypothesis

Back 6

Ionization state (alpha) of IC histidines, rather than the pH itself, is the critical variable during A-B balance regulation

Front 7

Bone buffers

Back 7

Buffering by exchange of ions

H+ <-> Na+, K+

HCO3-, CO3-, salts

Front 8

Urinary buffers

Back 8

HCO3- usually fully reabsorbed

Pi: HPO4-- -> H2PO4- (urine pH: up to 4.5)

NH3/NH4+

Front 9

Metabolic processes that generate A's & B's

Back 9

CO2 generation - volatile acid

Lactic acid, ketoacids - fixed acids

Organic anions -> bases (citrus juice paradox)

Protein catabolism -> acids

Organic phosphates, nucleic acids -> acids

Divalent cations -> salts => acids

Front 10

Alkaline tide

Back 10

For every H+ ion secreted (ex.: stomach), a HCO3- exits on the basolateral side & enters the blood

Front 11

Allowed pH range of urine

Back 11

4.5 - 8.5

-> to excrete all the acids produced in body, H+ must be excreted in a buffered form (Pi, NH3)

Front 12

NH4+ secretion

Back 12

Toxic -> very little can be in blood =>

Liver: α-ketoglutarate + NH4 -> glutamine

Kidney: reverse; α-ketoglutarate ->> 2 HCO3-

Corticopapillary gradient

Diffusion trapping in the CD

Front 13

Cellular remodelling

Back 13

CD intercalated cells switch b/n:

α: secrete acid

β: secrete HCO3-

Front 14

A-B balance vs. other ions

Back 14

Na/H exchanger

Indirect coupling in CD

=> V depletion/hyperaldosteronism -> alkalosis

K+ x H+ IC movement => hypo-/hyperkalemia -> IC x EC pH

K+ secretion -> EC acidosis

Front 15

Acidemia effects

Back 15

Respiration stimulus

Hyperkalemia -> ↓ heart fx

Metabolic a. -> bone dissolution

Alkalosis: opposite to acidosis, but also ↓ heart fx;

-> tetany

Front 16

Normal ranges for

pH, P(CO2), [HCO3-], PAG

Back 16

pH ~ 7.40

P(CO2) ~ 35-45 mmHg (-> respiratory)

[HCO3-] ~ 22-26 mEq/L (-> metabolic)

PAG ~ 8-12 mEq/L (albumin)

Front 17

Distinguishing b/w acute vs. chronic respiratory disorder

Back 17

Based on the degree of renal compensation (~ Δ[HCO3-])

Front 18

Plasma Anion Gap (PAG)

Back 18

PAG = [Na+] - [Cl-] - [HCO3-]

Front 19

Renal tubular acidosis

Back 19

Renal defect in H+ secretion

-> acidosis