Blood and Gas transport

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Blood and Gas transport
Chapter 9
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Functions of blood

• Coagulation
• Homeostasis
• Transport of
• Nutrients
• Metabolites
• Excretory products
• Hormones
• Cells
• Heat
• Force
• Blood gases

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Components of mammalian blood

• Plasma
• Liquid portion of blood
• Contains ions, proteins, hormones
• Cells
• Red blood cells
• Contain hemoglobin to carry oxygen
• White blood cells
• Platelets
• Important in blood clotting
• Hematocrit (Hemocrit)
• Percent of blood composed of cells

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Blood gas transport
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Gasses in water-Henrys Law of dissolved gases

• V aP
• V Volume of dissolved gas (ml/L) G
• a Bunsen solubility coefficient (varies with
  temperature and other solutes) S gas
• P Partial Pressure of gas (mmHg) Pgas

G Pgas x S gas
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Gasses in water-Henrys Law of dissolved gases

• V aP
• V Volume of dissolved gas (ml/L) G
• a Bunsen solubility coefficient (varies with
  temperature and other solutes) S gas
• P Partial Pressure of gas (mmHg) Pgas
• P pO2 lungs 95mmHg
• ?? at 37oC is 0.0315
• V 95 x 0.0315 2.99 ml/L (0.3ml)

G Pgas x S gas
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O2 transport in mammalian blood

• Solubility of O2 in blood (at 37oC) is about
  0.3ml/100ml (0.3ml)
• Total capacity of blood is about 20.5ml
• O2 is bound to hemoglobin (Hb) for transport in
  the blood
• Carrying capacity
• 201 ml O2L-1 blood in males
• 174 ml O2L-1 blood in females

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Respiratory Pigments
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Hemoglobin

• Tetramer 68kDa
• Oxyhemoglobin
• Deoxyhemoglobin
• Carbamino-hemoglobin-CO2
• Carboxy-hemoglobin-CO
• Met-hemoglobin-Fe3 (Ferric)

Porphyrin ring
2 ??subunits plus 2 ??subunits (adult) 2 ?
subunits (fetal) 2 ? subunits (embryonic)
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Carbamino-hemoglobin

• CO2 transport
• Amino terminus

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Carboxy-hemoglobin

• Carbon monoxide CO
• Binds to Fe2
• 200x affinity
• Color change
• Hyperbaric oxygen

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Methemoglobin

• Iron oxidized to Ferric form Fe3
• Nitrates, Chlorates
• Methemoglobin reductase
• lt1 in mammals
• Teleosts
• 25 winter
• 5 summer

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Hemoglobin O2 association/dissociation curve

• O2 Hb lt--gt HbO2
• Allosteric tetramer
• Reversible binding
• Affinity
• P50
• Variable affinities

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Cooperativity
Lamprey
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O2 Transport into Muscle

• Myoglobin (Mb) shuttles O2 from the cell membrane
  to the mitochondria
• Monomer
• Higher affinity for O2 than hemoglobin
• Even at low PO2
• Allows Mb to store O2

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Affinity

• Effects and benefits of changing affinity (p50)?

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O2-Hb Dissociation Curve Bohr Shift Effect of pH
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Small mammals display greater Bohr shift
Bohr Shift
Body Mass
i.e. mouse blood is more acid sensitive than
elephant blood
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Hemocyanins

• Bohr Shift
• Cancer magister (Dungeness crab)

• Limulus
• Reverse Bohr shift!

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Capacity
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Root Shift (pH)

• Teleost fish
• 2 types of hemoglobin

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O2-Hb Dissociation Curve Effect of Temperature

• Increased blood temperature results in a weaker
  Hb-O2 bond
• Rightward shift of curve
• Easier offloading of O2 at tissues
• Pigeons

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Effect of CO2

• Increased CO2 causes shift to .?
• Carbamino hemoglobin

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Blood bank

• Long term storage of blood affects affinity

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Factors affecting O2 transport

• Organic Phosphates
• 2,3-diphosphoglycerate mammals
• Inositol pentaphosphate birds
• ATP/GTP fish

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Developmental changes in hemoglobin in placental
mammals

• Two a-chains
• Embryonic ?
• Yolk sac
• Fetal ?
• Liver and spleen
• Adult ?
• Bone marrow and spleen

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Human pH 7.4
Fetal pig p5023 Adult Pig p5032
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Teleost Swim Bladder

• FW specific gravity 1.00 g/ml
• SW specific gravity 1.026 g/ml
• Fish specific gravity 1.07 g/ml
• Swim bladder volume ?
• Sharks Squalene
• Pelagic fish Swim bladder

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Slow 10 to 20 seconds
Fast 50msec
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Effects of altitude on affinity

• Interspecific
• Yak and cow
• Intrinsic differences in Hb
• Llama and camel
• Intrinsic differences in Hb
• Geese
• Vulture
• Subspecies of Peromyscus maniculatus
• High altitude strains had lower p50
• Second generation

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Effects of altitude on affinity

• Intraspecific
• NASA, USAF

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Altitude affects hemoglobin

• Below 4300m curve shifts to right (lower
  affinity)
• At 3000m, DPG is 10 higher than sea level
• Easier to unload O2
• Above 4300m curve shifts to left (higher
  affinity)
• Needed to load O2
• Variable levels of DPG in RBCs

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Experimental adjustment of rat affinities by drug
therapies to lower DPG levels

• Atmospheric Pressure233mmHg (8000m)
• pO2 46mmHg
• 90 minutes exposure
• Control group
• 8 of 10 died
• (p5037.3mmHg)
• Arterial O27 (20 is normal-PulseOx35)
• Experimental group
• 0 of 10 died
• (p5021mmHg)
• Arterial O214 (20 is normal-PulseOx70)

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Short term changes- Respiratory alkalosis Long
term changes- Hematocrit increases
Works up to 5500m
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Acclimation
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Burrowing animals

• O2 levels down to 6.
• CO2 levels up to 3.8
• Typically higher affinities
• Sciuridae
• Prairie dog p50 lower than squirrel-lower DPG
• Mole-decreased sensitivity to DPG
• Pangolin-lower DPG
• O2 capacities unchanged

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Diving animals

• Small whales, some pinnipeds and rodents
• Lungs used to store O2
• Higher affinity and Bohr shift
• Large whales and some pinnipeds
• Lungs not used to store O2
• No change in affinity, higher Bohr shift
• Reptiles
• Chrysemus
• Anoxia tolerant
• Low CO2 effect at low temperature
• Minimal Bohr shift at low temperature
• Crocodilians
• Acid insensitive
• Rapid turnaround

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Lactate accumulation in Weddell Seals
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Total body oxygen stores of diving mammals and
humans
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CO2 transport

• C6H1206 6O2 ---gt 6CO2 6H20
• CO2 H20lt---gtH2CO3 lt---gtHCO3- H
• Carbonic acid bicarbonate

5 0.005 (cold blooded) 95 (warm blooded)
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Carbonic Anhydrase

• Rate
• Inhibition

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Carbamino-hemoglobin

• Carbon dioxide
• Amino terminus
• CO2 transport

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Respiratory Quotient

• Production of CO2 leads to release of H that
  must be buffered by formation of carbamino
  compounds
• Therefore amount of CO2 produced is important
• Respiratory Quotient (RQ)
• CO2 produced/ O2 used
• Variable with fuel types

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Respiratory Quotient.Fats vs Carbohydrates

• Glucose
• C6H1206 6O2 6CO2 6H2O
• RQ 6/6 1.0
• Palmitic acid
• C16H3202 23O2 16CO2 16 H20
• RQ 16/23 0.7

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Estimation of Fuel Utilization

• Respiratory exchange ratio (RER or R)
• VCO2 / VO2
• Indicates fuel utilization
• 0.70 100 fat
• 0.85 50 fat, 50 CHO
• 1.00 100 CHO
• During steady state exercise
• VCO2 and VO2 reflective of O2 consumption and CO2
  production at the cellular level

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Blood CO2 and pH

• Air breathing vs. aquatic animals
• Air breathers have buildup of CO2 in blood
• Aquatic animals do not
• Amphibious animals?