Blood components and function Flashcards
How much iron is in the body at any one time?
3-5g
How is iron stored
Oxygen carrying globin - 70% haemoglobin, 5% myoglobin
Bound to other proteins e.g. cytochromes and transferrin
Sotrage as mostly ferritin 25%
What is ferritin? Where is it mostly found? How does it function?
‣ Many cells can produced apoferritin which binds iron and the complex with iron is known as ferritin
‣ Apoferritin is a huge protein with 24 polypeptide subunits and forms a miscelleof ferrid hydroxyphosphate containing as many as 4000 iron molecules and 50% of the ferritin weight can be iron. Under typical conditions 23% ferritin weight is iron
‣ When iron levels increase it binds to mRNA of apoferritin increasing translation of the protein –> occurs in mucosal cells to rapidly adapt to increased dietary iron to prevent over absorption or mucosal damage
Where is iron absorbed?
Enterocytes of duodenum and upper Jejenum
As Haem or as dietary irons alts
How is Haem absorbed
Direct specialised transport proteins
Haem is soluble pH >6
Absorbed by metallo porphyrin by mucosal cells and broken down in enterocytes
How is iron absorbed
Fe2+ is soluble and absorbed by facilitated diffusion - soluble up to pH 7.5, and the less acid the stomach prooudces the less it is absorbed.
Absorption by divalent metal transport (DMT) on apical membrane 0 under regulation
Fe 3+ precipitates in ph>3 envrionments, so cannot be absorbed. Acidity and ascorbic acid reduced Fe3+ to Fe2+ increasing its absorption. Ferric iron can be conerted by ferrireductase into ferrous form on apical mmebrane but need to be in a free unbound form
Which of Fe2+ and Fe3+ is more absorbed
Fe2+ is soluble and absorbed by facilitated diffusion - soluble up to pH 7.5, and the less acid the stomach prooudces the less it is absorbed.
Absorption by divalent metal transport (DMT) on apical membrane 0 under regulation
Fe 3+ precipitates in ph>3 envrionments, so cannot be absorbed. Acidity and ascorbic acid reduced Fe3+ to Fe2+ increasing its absorption. Ferric iron can be conerted by ferrireductase into ferrous form on apical mmebrane but need to be in a free unbound form
Once absorbed across apical membrane what happens to iron?
Stored and bound to ferritic in FERIC form
Ferrous iron transported via ferroportin out of he enterocyte. Converted to ferric iron at basolateral membrane, (by ferroxidase) thenn binds to transferrin as ferric iron (baseline 33% saturation)
What is the dialy requirement for iron
- Absorption total 0.6 - 1mg/day in adult male, 2.1mg/day in adult female (5-10% of dietary iron intake)
◦ Iron requirements in pregnancy increase by 1g leading to 6-7mg per day absorption from 20 weeks on as by 3rd trimester the foetus takes 4g/day itself
Regulation of iron is by
Basolateral membrane absorption block - reduced ferritin, reduced transferrin
Hepcidin inhibits ferroportin
What form is iron in when bound to ferritin?
Fe3+ ferric
What form is iron in when being transported around the body?
Fe3+ ferric
What is haemosiderin
◦ However if iron stores are high cells accumulate haemosiderin an insoluble cellular iron composed of partially degraded ferritin
What structurally is transferrin?
◦ Transferrin is a beta 1 globulin produced in the liver
What is a platelet
Cellualr component of the haemostatic response
What is the process of platelet formation? From what do they originally form?
Cellular component of the haemostatic response
Progressed from common myeloid prognitor stem cell
How is thrombopoiesis stimulated?
- Megakaryocytes are proudced from differentiation of this stem cell in response to thrombopoeitin
◦ Thrombopoeitn accelarates all stages of the pathway to plt development, is produced 90% in the liver, 10% in kidney, in response to stress and low platelets, and inhibited by mature platelets.
How do megakaryocytes turn inot platelets?
- Megakaryocytes undergo a process called endomitosis –> DNA replication without nuclear or cellular division causing massive polypoid proliferation
- Terminally mature megakaryocytes extend protoplasmic extensions filled with usual platelet components (mitochondria, ribosomes, endoplasmic reticulum, secretory granules, tubular stuctural systems) into sinusoidal vessels where cytoplasm separates into beads and they are pinched off forming platelets
- Megakaryocytes apoptose when cytoplasm exhausted
How long does it take to make a platelet
8-10 days
How many platelets are made per day?
15-40 x 10^9 produced per day
How long does a platelet survive
7-10 days
How are old platelets removed
reticuloendothelial system
What are usual platelet components
‣ Mitochondria
‣ Ribosomes
‣ Short lengths of rough endoplasmic reticulum
‣ Secretery granules
‣ Surface connected canalicular system
‣ Dense tubular systems
How big is platelet
.5 - 3 micrometres
Does a platelet have a nucleus
no
What shape is a platelet
Disc
How does a platelet make energy
Anaerobic glycolysis with some Krebs citric acid cycle aerobioc metabolism
What granules are within a platelet
‣ Dense bodies
* ADP, ATP, serotonin - contribute to platelet aggregation
‣ Alpha granules
* Platelet factor 4 + platelet derived growth factor
* Beta Thromboglobulin + Thrombospondin
* Fibrinogen + fibronectin
* VWF
What is in an alpha granule?
‣ Dense bodies
* ADP, ATP, serotonin - contribute to platelet aggregation
‣ Alpha granules
* Platelet factor 4 + platelet derived growth factor
* Beta Thromboglobulin + Thrombospondin
* Fibrinogen + fibronectin
* VWF
What is in a dense body?
‣ Dense bodies
* ADP, ATP, serotonin - contribute to platelet aggregation
‣ Alpha granules
* Platelet factor 4 + platelet derived growth factor
* Beta Thromboglobulin + Thrombospondin
* Fibrinogen + fibronectin
* VWF
What contributes to the ultrastructure of a platelet
◦ Microtubules and surface-connected canaliculi
‣ Circumferential microtubules maintain resting discoid shape
‣ Contractile protein system of micro filaments throughout the cytoplasm - activation shape change
‣ Dense tubular system is the residual ER - rich in Ca, ATPase, adenyl cyclase, acetyl cholinesterase, peroxidase, glucose 6 phosphatase
* Site of synthesis of PG and TXA2
What is the surface of platelets like>
◦ External glycocalyx layer (thick, 20-30nm) - thicker than other cellular glycocalyces, negative charge to repel other platelets and also procoagulant molecules
What are the invaginations of platelet membranes called? Function?
Canaliculi
Increased the surface area
‣ Double layer of lipid and phospholipid covered by protein ‣ Membrane phospholipids source of AA, platelet activating factor and platelet factor 3 important for activation of factor X and prothrombin
What are the significant proteins on the membrane of platelets that bind during coagulation
◦ outer layer of membrane glycoproteins on Glycocalyx important for adhesions nd aggregation
‣ GP 1a - bonds to collagen
‣ GP 1b, 2b, 3a attach to VWF —> subendotheliam
‣ GP 2b/3a bonds to fibrinogen
What is the function of platelets
Initial platelet plug in primary haemostasis
- Platelet plug - activating and aggregating other platelets
- Coagulation cascade - augmentin via degranulation AND providing a surface area for it to occur
- Vasoconstriction
what activates a platelet
Collagen
Exposed by damaged endothelium.
Adrenaline
ADP
Thrombin
What happens to a platelet that has been activated
Exocytosis of granules
Activation of membrane phospholipase A2 to form thromboxane A2
Deformation from a disc to a sphere with long projections
Promotion of the coagulation cascade
Change in glycoprotein (GP) expression by the action of ADP:
ADP antagonists (e.g. clopidogrel) prevent expression of the GPIIb/IIIa complex.
GP Ib/IIb/IIIa facilitate platelet attachment to vWF
vWF also binds to sub-endothelial connective tissue.
GP IIb/IIIa are also receptors for fibrinogen, which encourages platelet aggregation
How do platelets bind together
Exocytosis of granules
Activation of membrane phospholipase A2 to form thromboxane A2
Deformation from a disc to a sphere with long projections
Promotion of the coagulation cascade
Change in glycoprotein (GP) expression by the action of ADP:
ADP antagonists (e.g. clopidogrel) prevent expression of the GPIIb/IIIa complex.
GP Ib/IIb/IIIa facilitate platelet attachment to vWF
vWF also binds to sub-endothelial connective tissue.
GP IIb/IIIa are also receptors for fibrinogen, which encourages platelet aggregation
What is the important component on platelet cell surfaces for clotting factor binding
Phosphatidylserine
Red cell production is stimulated by?
EPO
What is the half life of EP{O
6-9 hours
EPO comes from
90% synthesised in the kidney peritubular complex; 10% in liver
Where are red cells produced in the body? How does this change over time?
◦ Embryonic development migrates from mesenchymal stem cells in the yolk sac —> liver and spleen during late first, second trimester —> bone marrow in mid third trimester and onwards
◦ First 5 years of life exclusive bone marrow production, with gradual replacement to just central skeleten regions in the vertebrae, pelvis, ribs, sternum and skull as well as the proximal femur and humerus
What is a progenitor cell for red cell production
Common pleuripotent stem cell –> differeniates into myeloid and lymphoid stem cells –> myeloid stem cell can branch into myeloid precurser cells such as erythroblast colony forming unit –> proerythrobalst
How long does it take to make a red cell
5 days to a reticulocyte
7 days to a fully mature RBC
How does a RBC precurser become a red cell?
Proerythroblast synthesises haemoglobin before it gives rise to smaller normoblasts with more Hb and more condense nuclar chromatin
Eventual nucleus extrusion by the later erythroblast forming reticulocyte which enters circulation
Reticulocytes contain RNA and ribosomes and can sythesize further haemoglobin circulating for 1-2 days before ribosomes are exccluded and maturation is complete
What role to DNA nad folic acid have in RBC production?
Necssary for DNA formation - thymidine triphosphate
Deficiency resulting in large immature and fragile RBCs with short half lives
Red cell shape and size? Why is this an advantage?
- Biconcave disc
◦ 6-8 microm wide, 2 microm thick
◦ Large surface area relative to volume - promotes gaseous diffusion into the cell, minimal diffusion distance from cell centre
How is a red cell deformable? WHy si this important?
◦ Cytoskeletal reversible deformability - squeeze through capillaries, Band 3 protein, spectrin and actin particularly important components
◦ Maximal laminar flow as less prone to rotation during flow in large vessels
What internal contents does a red ell have
- Anucleate, no cellular organelles e.g. mitochondria, Golgi apparatus, endoplasmic reticulum
◦ Maximising space for Hb (330g/L) - Contains large quantities of haemoglobin + carbonic anhydrase
◦ haemoglobin is kept in cells as otherwise it diffuses into tissues and through the glomerulus
◦ Carbonic anhydrase increases rate of carbonic acid formation from water and CO2 by several thousand times
Red cell membrane is made up of? 2 key proteins? What charge does it have?
◦ Bipolar lipid layer containing enzymes, antigens, structural and contractile proteins
◦ 50% protein, 40% fat, 10% carbohydrate
◦ Glycocalyx on the outer surface of the membrane is rich in carbohydrates
◦ Proteins peripheral or integral- spectrin , actin, ankyrin, band 4.1 are the major ones forming a lattice on the inner side of the membrane maintaining the biconacave shape
◦ Negative surface charge preventing clumping agglutination
How does a red cell generate energy
No organelles (mitochondria) therefore glycolytic pathway
Called the Emden Meyehof pathway
- Generates NADH
- One molecule of glucose –> 2x pyruvate –> ATP and NADH
- NADH then used by lactate dehydrogenase to convert pyruvate to lactate
What is the Embden Meyehoff apthway
No organelles (mitochondria) therefore glycolytic pathway
Called the Emden Meyehof pathway
- Generates NADH
- One molecule of glucose –> 2x pyruvate –> ATP and NADH
- NADH then used by lactate dehydrogenase to convert pyruvate to lactate
How does a red cell generate energy? What is the eponymous name for this
No organelles (mitochondria) therefore glycolytic pathway
Called the Emden Meyehof pathway
- Generates NADH
- One molecule of glucose –> 2x pyruvate –> ATP and NADH
- NADH then used by lactate dehydrogenase to convert pyruvate to lactate
What 3 metabolic shunts are critical for red cells
- Methaemoglobin reductase - uses NADH to reduce methaemoglobin returning NAD+
- Hexose monophosphate shunt - produces NADPH converting oxidised glutathione to reduced glutathione used as an antioxidant in the cell
- LueBering Rapaport shunt producing 2,3 DPG from 1,3 diphosphoglycerate before it is turned to pyrvuate. This is reversible
How is 2,3 DPG created
- LueBering Rapaport shunt producing 2,3 DPG from 1,3 diphosphoglycerate before it is turned to pyrvuate. This is reversible
How is antioxidation performed in the red cell?
- Hexose monophosphate shunt - produces NADPH converting oxidised glutathione to reduced glutathione used as an antioxidant in the cell
What is the LueBering Rapaport shunt?
- LueBering Rapaport shunt producing 2,3 DPG from 1,3 diphosphoglycerate before it is turned to pyrvuate. This is reversible
What is the hexose monophosphate shunt
- Hexose monophosphate shunt - produces NADPH converting oxidised glutathione to reduced glutathione used as an antioxidant in the cell
What % of buffering qualities of the blood does Hb provide
◦ Hb acts as a buffer within RBC both through binding to CO2 and H+
‣ 50-60% of buffering qualities of the blood
What 3 aspects of acid base does a red cell offer
◦ Very high quantities of intracellular carbonic anhydrase
‣ Bicarbonate buffering
‣ Bicarbonate storage and transport of CO2
◦ Hb acts as a buffer within RBC both through binding to CO2 and H+
‣ 50-60% of buffering qualities of the blood
◦ Mitigation of pH change in peripheral circulation thorugh Hamburger effect
‣ pH would change far more if not for the buffering effect of Hb and the intracellular chloride shift
What is the lifespan of a red cell? why? How is this identified? How is it actually removed
120 days
- With senescence
◦ With aging glycolysis and hence ATP formation decreases —> reduced maintenance of cellular integrity and reduced deformability
◦ Express abnormal proteins on cell surface, coated in autologous anti Band 3 IgG (opsonin), reversal of membrane phosphatidylserine - Removed by phagocytosis in reticuloendothelial system of the spleen/liver (90%) and bone marrow as insufficiently deformable to navigate the tight sinusoids
◦ 10% spontaneous haemolyse
What happens to a red cell over time
◦ Over time decrease in density and size
◦ Enzyme activity decreases especially metabolic enzymes
◦ Covered in antibodies
◦ Denatured and irreversible oxidised proteins including Hb
- With senescence
◦ With aging glycolysis and hence ATP formation decreases —> reduced maintenance of cellular integrity and reduced deformability
◦ Express abnormal proteins on cell surface, coated in autologous anti Band 3 IgG (opsonin), reversal of membrane phosphatidylserine
How is a red cell removed from circulation
- Removed by phagocytosis in reticuloendothelial system of the spleen/liver (90%) and bone marrow as insufficiently deformable to navigate the tight sinusoids
◦ 10% spontaneous haemolyse
How is globin produced?
Subunits synthesed in ribosomes in the cytosol of immature RBC
Haem is synthesed where in the erythroblast?
Mitochondria
How is a haem made
Protoporphryn ring is formed by glycine + vitamin B6 + succinyl CoA –> combining with ferrous iron to form Haem
What joins the 4 rings surrounding Fe
Methenyl bridges - 4
Forming an Iron tetrapyrrole
What is the structure of ahemoglobin described as
tetramer
Metalloprotein
What is the rate limiting step of haemoglobin production?
ALA synthase which is the first step
(delta aminolaevulinic acid synthetase)
Haem inhibits this enzymes
What is the final step in haemoglobin production
Combination of the protoporphryin ring and the ferrous iron
Where does Haem combined with haemoglobin
RIbosomes
Haemoglobin moelcular weight
65 000 daltons similar to albumin
What is the structure of haemoglobin
Quaternary structure/tetramer containing 4 polypeptide chains each with a Haem group
How does the structure of Haemoglobin change between fully oxygenated and fully deoxygenated
positive cooperativity, each binding of oxygen to a monomer causes a conformational change in Globin increasing affinity for the binding of the next O2 –> transitioning from T (tense) deoxygenated state to R (relaxed) oxygenated state through intermediate states producing the sigmoid shaped oxygen/haemoglobin dissociation curve
◦ The relaxed state - one pair of alphabeta subunits appears rotated by 15 degrees with respect to all other subunits
What does 2,3 DPG do to haemoglobin
◦ When oxygen is unloaded the beta chains are pulled apart so that 2,3 Diphosphoglycerate enters the molecule and decreases affinity of Hb for oxygen - stabilises the deoxygenated state
Haem group is what sturcture
Flat porphyrin ring
Is Haem hydrophobic or hydrophilic
Iron at the centre is hydrophobic
Methyl groups on the outside are hydrophobic
What is iron bound to at the centre?
4 sites as part of the Haem group
2 available binding sites remain –> 1 for globin via imidazole side chain and another for oxygen/carbon monoxide, nitric oxide and hydrogen sulfide
What 4 substances can bind to the iron at centre of Haem groups
oxygen/carbon monoxide, nitric oxide and hydrogen sulfide
What are the steps in Haemoglobin breakdown?
Haem in microsomes broken down vai oxidation to Biliverdin + ferric iron + carbon monoxide
Biliverdin reductase converts biliverdin to bilirubin
Bilirubin UDP gluronyl transferase conjugates bilirubin to bilirubin diglucoronide
This can be metabolised by gut bacteria to urobilinogen and then to stercobilin
What is the first step in haemoglobin breakdown
Protoporphyrin ring is opened by haem oxygenase cleaving the alpah methene bridge of the porphyrin
Haem in microsomes broken down vai oxidation (Haem oxygenase) to Biliverdin + ferric iron + carbon monoxide
Why is it normal to have some carbon monoxide in the blood
Haem in microsomes broken down vai oxidation to Biliverdin + ferric iron + carbon monoxide
What structure does adult haemoglobin have
2 alpha and 2 beta chains forming 2 identical alpha beta dimers
What is the structure of foetal Hb
2 alpha and 2 gamma
1% of adult haemoglobin
What are the 4 functions of haemoglobin
- Oxygen transport
◦ Increased oxygen carrying capacity of blood by 50-100x
◦ Affinity for O2 increased under conditions of high PO2 and decreased under conditions of low PO2 enhancing loading in the lungs and unloading in the tissues of oxygen - CO2 transport
◦ 10-20% of total CO2 carriage as carbamino compounds
◦ Deoxygenated haemoglobin has a higher affinity for CO2 - Haldane effect; and releases it when it becomes oxygenated due to reduced affinity (reverse Haldane effect) - Buffer - bonding CO2 reduces CO2 dissolved and subsequent H+ ion creation
◦ Additionally bonds to H+ directly acting as a mild buffer via histidine residues with pKa 6.8 - act as proton acceptors, and this buffering capacity is highest in its deoxygenated state
◦ Accounts for 50-60% of the buffering capacity of the blood - Nitrous oxide scavenger
◦ NO binds to ferrous Fe2+ iron with great affinity and this is the most important mechanism for limiting nitric oxide bioactivity regulating regional blood flow
◦ Affinity of binding reduced by dexoygenation resulting in release of nitric oxide - release thus increased by tissue hypoxia
◦ Clinically important in hypoxic pulmonary vasoconstriction, pulmonary hypertension in polycythaemia and sickle cell vasoconstrictive crises
What does Hb do to NO
- Oxygen transport
◦ Increased oxygen carrying capacity of blood by 50-100x
◦ Affinity for O2 increased under conditions of high PO2 and decreased under conditions of low PO2 enhancing loading in the lungs and unloading in the tissues of oxygen - CO2 transport
◦ 10-20% of total CO2 carriage as carbamino compounds
◦ Deoxygenated haemoglobin has a higher affinity for CO2 - Haldane effect; and releases it when it becomes oxygenated due to reduced affinity (reverse Haldane effect) - Buffer - bonding CO2 reduces CO2 dissolved and subsequent H+ ion creation
◦ Additionally bonds to H+ directly acting as a mild buffer via histidine residues with pKa 6.8 - act as proton acceptors, and this buffering capacity is highest in its deoxygenated state
◦ Accounts for 50-60% of the buffering capacity of the blood - Nitrous oxide scavenger
◦ NO binds to ferrous Fe2+ iron with great affinity and this is the most important mechanism for limiting nitric oxide bioactivity regulating regional blood flow
◦ Affinity of binding reduced by dexoygenation resulting in release of nitric oxide - release thus increased by tissue hypoxia
◦ Clinically important in hypoxic pulmonary vasoconstriction, pulmonary hypertension in polycythaemia and sickle cell vasoconstrictive crises
What happens to haemoglobin if free in the blood?
- Unbound Hb will degrade into alpha beta heterodimers which allows filtration, and penetration into glycocalyx
- Small amounts of free Hb may be released into plasma and haptoglobin (an alpha2 globulin) binds to the globin moeity
◦ Haptoglobin huge protein (150kDa) therefore when bound this limits Hb passage into other tissues, preventing iron loss
◦ Haemopexin binds to Haem (post degredation in blood stream) where haptoglobin is saturated (and thus was unable to bind it earlier) - Beta glycoprotein
◦ This complex is then captured by reticuloendothelial macrophages via endocytosis
‣ Haemoglobin in senescent erythrocytes is reclaimed by macrophages
What protein scavenges haemoglobin that is free? What type of protein is it? What takes its role if this is saturated?
- Unbound Hb will degrade into alpha beta heterodimers which allows filtration, and penetration into glycocalyx
- Small amounts of free Hb may be released into plasma and haptoglobin (an alpha2 globulin) binds to the globin moeity
◦ Haptoglobin huge protein (150kDa) therefore when bound this limits Hb passage into other tissues, preventing iron loss
◦ Haemopexin binds to Haem (post degredation in blood stream) where haptoglobin is saturated (and thus was unable to bind it earlier) - Beta glycoprotein
◦ This complex is then captured by reticuloendothelial macrophages via endocytosis
‣ Haemoglobin in senescent erythrocytes is reclaimed by macrophages
Features of a RBC that facilitate transport of oxygen - structure 3
Biconcave structure - maximised surface area, minimised diffusion distance
Enhanced deformability alowing RBC to deliver oxygen to very small capillary systems
Deformability also aids in laminar flow reducing the viscocity in small vessels and reducing resisatnce
Lack of internal organelles allow for this deformability but also maximise Hb
RBC also protects haemoglobin itself from being broken down in circulation
Aside from positive cooperativitiy what other features of Hb optimise its ability ot transport oxygen
2,3 DPG, CO2 and H+ all result in stabilization of the deoxygenated haemoglobin –> therefore optimising its release in sites of high metabolic requirement
Bohr effect –> increased CO2 reduces oxygen affinity
What metabolic features optimise RBC as a transport medium for oxygen
- RBC does not contain mitochondria and therefore is the ideal transport agent as it does not consume the oxygen it is meant to transport , instead generating ATP via Embden Meyerhof pathway or glycolytic pathway
- Important shunts off this include
◦ 2,3 DPG via Rapoport Luebering shunt previously mentioned
◦ Hexose monophosphate shunt generating NADPH protecting RBC from oxidative damage
◦ Methaemoglobin reductase pathway borrowing NADH from glycolysis to reduce methaemoglobin back to haemoglobin maximising oxygen delivery in the context of Haem units being oxidised
What is the p50 for foetal haemoglobin
19mmHg
What two features optimise foetal gas transfer
◦ The double Bohr effect:
‣ Raised placental CO2 and acidic placental pH decrease the oxygen affinity of maternal haemoglobin, enhancing O2 release (first effect)
‣ The decreasing PCO2 in foetal blood increases its affinity for oxygen (second effect)
◦ The double Haldane effect:
‣ As it becomes oxygenated, foetal haemoglobin releases CO2 (first effect)
‣ As maternal haemoglobin becomes deoxygenated, it binds more CO2 (second effect)
◦ The combination of these effects increases the separation between oxygen-haemoglobin dissociation curves of foetal and maternal haemoglobin (HbF is left-shifted and HbA is right-shifted)
Define plasma
Cell free liquid component of blood
Serum
Remaining fluid after blood has been allowed to clot and the clot is removed (clotting factos and fibrinogen removed)
How is serum different from plasma
Plasma is the cell free content of blood
Serum is the liquid left once the blood has been allowed to clot
WHat % of body weight is plasma?
4%
How much plasma does one person have?
40-50mL/kg
3.5L
What % of blood volume is plasma usuallyl
55%
What is a normal haematocrit
45%
What is the composition of plasma
92% water
7% protein
1% solutes by volume
Gases <1% by volume
What proteins are in blood? (3 most common) What % of plasma do they make up?
roteins 7% of volume, 70-90g/L (350-450g in avg person),
◦ Albumin 80% of proteins
◦ Globulin
◦ Fibrinogen
When solutes are considered in blood what divisions can be made?
Electrolytes/ions 260-280mmol/L
- Cations
- Anions
Low molecular weight non electrolytes
- Carbohydrates
- urea, uric acid
- Lipids
- Hormones
- Vitamins
What is the concentration of plasma proteins?>
60-80g/L
What are the 4 major non albumin proteins in blood
Alpha globulins
- Alpha 1 globulins - alpha antitrupsin, AFP, alpha 1 acid glycoprotein
- ALpha 2 globulins - macroglobulin, prothrombin, haptoglobin, ceruloplasmin
Beta globulins
- Transferin
- CRP
Gamma glkobulins
Fibrinogen
What are the 4 main alpha 1 globulins
‣ ALpha 1 anti trypsin - serin protease inhibitor
* Produced in the liver
* Potent inhibitor of trypsin, chymotrypsin, activated plasmin and other proteases
‣ Alpha 1 foetoprotein
‣ Alpha 1 lipoproteins - associated with alpha 1 globulins and contain 45-55% lipid
* Chylomicrons (80-90% TG, 1-2% proteins)
* VLDLs - transport endogenous TG from liver to peripheral tissues for storage
* LDL - transport cholesterol to the tissues
* HDL - return cholesterol to the liver
‣ ALpha 1 acid GP - acute phase protein in low concentrations, binds to basic drugs
What are the 2 most important proteins for binding of acidic and basic drugs?
Albumin - acidic drugs
Alpha 1 acid glycoprotein - basic drugs
What family do lipoproteins belong to
‣ ALpha 1 anti trypsin - serin protease inhibitor
* Produced in the liver
* Potent inhibitor of trypsin, chymotrypsin, activated plasmin and other proteases
‣ Alpha 1 foetoprotein
‣ Alpha 1 lipoproteins - associated with alpha 1 globulins and contain 45-55% lipid
* Chylomicrons (80-90% TG, 1-2% proteins)
* VLDLs - transport endogenous TG from liver to peripheral tissues for storage
* LDL - transport cholesterol to the tissues
* HDL - return cholesterol to the liver
‣ ALpha 1 acid GP - acute phase protein in low concentrations, binds to basic drugs
What are 2 examples of alpha 2 globulins?
‣ Alpha 2 macroglobulin - protease inhibitor in plasma, major protein 80% of this faction
* Inhibitory functions on plasma trypsin, chymotrypsin, plasmin
* Inhibit proteases produced by infectious organisms
‣ Prothrombin - 60% of extracellular pool in plasma, 40% extra vascular
* Rapid turnover
‣ Haptoglobin - globulins binding free Hb and transporting to the liver
‣ Ceruloplasmin - plasma protein carrying copper and is produced in the liver
* Oxidase enzyme oxidising ferrous to ferric iron before binding of iron to transferrin
* Acute phase protein
* ?free radical scaveneger
Prothrombin is what type of protein
ALpha 2 globulin
Haptoglobin is what type of protein?
Alpha 2 globulin
Beta globulin include
Transferrin
What % do immunoglobulins reside in blood
◦ Immunoglobulins produced by plasma cells of bone marrow, spleen, lymph nodes and gut
◦ IgG 76% - binds to complement, acts against soluble antigens
◦ IgA - 16% of circulating antibodies in zero mucous, does not fix complement and protects against secretory musical surfaces
◦ IgM - 7%, rapidly synthesised, can fix complement to break down foreign surfaces
◦ IgE - very low concentrations
Fibrinogen is what size protein
340kDa
What is the normal concentration of fibrinogen
1.5 -4g/L
What forms can fibrinogen be found in?
‣ Soluble form —> ligand for activated GP 2b/3a on platelets and forms cross bridges for aggregation
‣ When cleaved by thrombin converted to fibrin polymerising into insoluble or stabilising plug of clot
General functions of proteins in the blood
- Primary role in the plasma:
◦ Oncotic function: albumin maintains oncotic pressure at ~ 25 mmHg as a part of Starling forces regulating fluid exchange in microcirculation
◦ Coagulation: fibrinogen and the clotting cascade enzymes
◦ Buffering: proteins contribute about 20% of the non-bicarbonate buffering; mainly done by Hb - Immune function: immunoglobulins and complement
- Signalling function: endocrine and paracrine hormones, eg. insulin
- Transport function:
◦ Transport of macronutrients, eg. lipoproteins
◦ Transport of micronutrients, eg. transferrin
◦ Transport of hormones, eg. thyroid-binding globulin - Non-physiological functions of clinical value:
◦ Drug binding, eg. albumin and α-1 acid glycoprotein
◦ Biomarker, eg. myoglobin, procalcitonin, CRP, light chains
What transport functions do plasma proteins have?
- Primary role in the plasma:
◦ Oncotic function: albumin maintains oncotic pressure at ~ 25 mmHg as a part of Starling forces regulating fluid exchange in microcirculation
◦ Coagulation: fibrinogen and the clotting cascade enzymes
◦ Buffering: proteins contribute about 20% of the non-bicarbonate buffering; mainly done by Hb - Immune function: immunoglobulins and complement
- Signalling function: endocrine and paracrine hormones, eg. insulin
- Transport function:
◦ Transport of macronutrients, eg. lipoproteins
◦ Transport of micronutrients, eg. transferrin
◦ Transport of hormones, eg. thyroid-binding globulin - Non-physiological functions of clinical value:
◦ Drug binding, eg. albumin and α-1 acid glycoprotein
◦ Biomarker, eg. myoglobin, procalcitonin, CRP, light chains
What are the 3 most important roles of protein in plasma?
- Primary role in the plasma:
◦ Oncotic function: albumin maintains oncotic pressure at ~ 25 mmHg as a part of Starling forces regulating fluid exchange in microcirculation
◦ Coagulation: fibrinogen and the clotting cascade enzymes
◦ Buffering: proteins contribute about 20% of the non-bicarbonate buffering; mainly done by Hb - Immune function: immunoglobulins and complement
- Signalling function: endocrine and paracrine hormones, eg. insulin
- Transport function:
◦ Transport of macronutrients, eg. lipoproteins
◦ Transport of micronutrients, eg. transferrin
◦ Transport of hormones, eg. thyroid-binding globulin - Non-physiological functions of clinical value:
◦ Drug binding, eg. albumin and α-1 acid glycoprotein
◦ Biomarker, eg. myoglobin, procalcitonin, CRP, light chains
What are the main functions of albumin
- Transport protein
- Colloid osmotic pressure
- Antithrombotic effect
4/ Free radical scavenger - Nitric oxide metabolism
6/ Buffer
What does albumin do as a transport protein?
2 drugs
2 hormones
2 solutes
2 electrolytes
- Carrier/transport protein - for acid substances including drugs (warfarin/diazepam), hormones (steriods and thyroxine) and fatty acids, bile salts, bilirubin, calcium and magnesium. Renders these substances increasingly water soluble allowing for biological concentrations to be delivered to effect sites
What % of osmotic pressure does albumin provide?
- Contributes 80% of plasma colloid osmotic pressure a key component of starlings forces oncotic maintaining fluid balance between intravascular and extra vascular spaces balancing hydrostatic pressure differences
What non transport and non oncitc functions do albumin have (4)
- Antithrombotic effect - inhibiting platelet aggregation
- Free radical scavenger
- Nitric oxide metabolism as a source of sulfhydryl groups
- Buffer - amphoteric and dissociates with a net negative charge contributing 15% to total buffering capacity of the blood via weak ionisation of COOH and NH2 groups
What si the baseline albumin concentration
40g/L
Where is albumin produced? How much per day?
Liver
10g per day
How is albumin distributed?
1/3 intravascular
1/6 non exchangeable in skin and muscle
50% interstitial - fast to viscera and slow to muscles (4.5% per hour)
How much albumin is turned over per day
4%
What factors increase albumin syntheiss?
Hihg protein, high calory
Decreased colloid osmotic rpessure
Hormones - GH, corticosteriods, insulin
Factors reducing albumin syntheiss
Protein/malnutrition
Liver disease
Inflammation
Sepsis
Trauma
Diabetes
Increased plasma oncotic pressure
What is the consequence of giving 500ml of 4% albumin
Isoosmolar, isooncotic
- Infused volume should remain in circulation for some time, albumin oncotic pressure 80% of total
Adds osmotic pressure through sodium atttraction (Gibbs Donnan)
As 4% albumin is isooncotic it DOES NOT mobilise fluid from anywhere else, but prevents redistribution –> doubles the amount that remains intravascular (50% instead of NaCL where 25% remains intrravascular)
Therefore of 500ml may change circulatory reflexes
Minimal change in osmolality
Minimal change in biochemistry
Some antioxidant scavenging
Nd binding of small moelcules
How is 4% albumin different to NaCl when infusing 500ml
As 4% albumin is isooncotic it DOES NOT mobilise fluid from anywhere else, but prevents redistribution –> doubles the amount that remains intravascular (50% instead of NaCL where 25% remains intrravascular)
When you give 20% 100ml of albumin what is the effect on osmolality?
Increased by 10 mOsm/kg and 100ml of fluid added
Albumin redistribution rate
4.5% per hour
What does 20g of albumin in 100mls do to fluid balance?
- Intersitital fluid loses 32mls, intracellular fluid loses 88mls, intravascular gains 100mls (infusion) + ~120mls of redistirbution
Per g of albumin what fluid is gained in general
◦ 8-10ml per 1g of albumin retained intravascular (depending on capillary permeability to albumin) and maximal 30 minutes post infusion –> ~approximately an additional 220mls gained once redistribution occurs)
What effect does 20% 100ml of albumin have on osmolality?
◦ Water dilutes intravascular space, serum osmolality drops 15mosm/L (6%) based on water movement only; however the increased net anionic charge attracts positively charged ions (Gibbs Doonan effect)
◦ If this redistirbution of positive charge did not occur the osmolality change would be enough to cause reduced release of ADH and diuresis
How would you categorise the effects of anaemia
Based on oxygen delivery
Total blood oxygen delivery (DO2) = CO × CaO2,
and CaO2 = (sO2 × ceHb × BO2 ) + (PaO2 × 0.03)
where:
ceHb = the effective haemoglobin concentration
CO = cardiac output
PaO2 = the partial pressure of oxygen in arterial gas
0.03 = the content, in ml/L/mmHg, of dissolved oxygen in blood
BO2 = the maximum amount of Hb-bound O2 per unit volume of blood (normally 1.39)
sO2 = oxygen saturation
Baseline oxygen delivery to tissues is?
At baseline with Hb 150 –> oxygen carrying capacity 200ml/L –> 5L/min cardiac output –> 1000ml/min (15ml/kg/min). Oxygen consumption is 3.5ml/kg/min (250mls/min). Hb 37.5 is the limit below which demand < supply if cardiac output the same. However physiological responses temporise this if gradual.
What is the lower limit of haemoglobin below which oxygen delivery would be not enough to meet demand where cardiac output remains unaltered?
At baseline with Hb 150 –> oxygen carrying capacity 200ml/L –> 5L/min cardiac output –> 1000ml/min (15ml/kg/min). Oxygen consumption is 3.5ml/kg/min (250mls/min). Hb 37.5 is the limit below which demand < supply if cardiac output the same. However physiological responses temporise this if gradual.
How is anaemia detected?
◦ Anaemia is detected by aortic arch chemoreceptors
‣ They sense oxygen content of the blood, rather than the PaO2 –> oxygen content of blood due to dissolved O2 is 0.03ml/mmHg/L i.e. 22.8ml per litre maximum at 100% FiO2; and generally 3ml
‣ Vagal afferents transmit this information to the nucleus of the solitary tract
‣ The efferent arc of this reflex is mediated by the vagus nerve and the sympathetic nervous system
◦ Reduced oxygen carrying content detected by renal cells secreting EPO
‣ Stimulates differentiation and release of RBCs into blood stream
What are the cardiovascular effects of acute anaemia?
◦ Tachycardia - Vagally mediated tachycardia is partly due to direct aortic arch chemoreceptor activity and partly due to baroreflex activation
◦ Increased stroke volume - Baroreflex activation is due to systemic vasodilation
◦ Increased cardiac output - Baroreflex activation is due to systemic vasodilation
◦ Decreased peripheral vascular resistance (no autonomic factors involved)
‣ Systemic vasodilation which is mediated by nitric oxide, as the result of decreased oxygen delivery to the tissues (a part of the normal metabolic autoregulation of regional blood flow)
‣ Decreased blood viscosity, as viscosity is an important determinant of peripheral vascular resistance via the Hagen Poiseulle equation (R = 8nl/pixr*4
If Hb dropped form 140 –> 50 what regulatory responses would be involved if you remained isovolaemic?
◦ Tachycardia - Vagally mediated tachycardia is partly due to direct aortic arch chemoreceptor activity and partly due to baroreflex activation
◦ Increased stroke volume - Baroreflex activation is due to systemic vasodilation
◦ Increased cardiac output - Baroreflex activation is due to systemic vasodilation
◦ Decreased peripheral vascular resistance (no autonomic factors involved)
‣ Systemic vasodilation which is mediated by nitric oxide, as the result of decreased oxygen delivery to the tissues (a part of the normal metabolic autoregulation of regional blood flow)
‣ Decreased blood viscosity, as viscosity is an important determinant of peripheral vascular resistance via the Hagen Poiseulle equation (R = 8nl/pixr*4
Oxygen extraction ratio only slightly decreased from 75 –> 70%
What long term adaption is seen to chronic anaemia
Chronic baroreceptor activation
Salt retention by aldosterone
Body water volume expansion by vasopressin and aldosterone
Angiogenesis to increase capillaries and reduce diffusion distance
Chronic vasodilation
