Erythrocytes Flashcards by Sara Prent

mammalian shape of RBC

discocyte (biconcave disc)

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Which in general have a higher RBC mean cell volume: mammals or nonmammals?

nonmammals

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Increased total RBC count –> MCV? (In general)

decreases. As number of RBCs increases, they usually also decrease in size

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“drepanocyte” means:

sickle shaped. i.e. - deer blood

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“dacrocyte” means:

tear shaped. i.e. - goat blood

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Camelids have what shape RBC?

elliptocytes

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Birds have what shape RBC?

ovalocyte

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pigs have what shape RBC?

echinocyte

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What causes sickling of RBC?

Single amino acid substitution. Also, a pH drop and oxygen can potentiate sickling

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What can cause echinocyte shape in RBC?

1) excess anticoagulant in sample
2) ATP depletion with prolonged storage
3) addition of fatty acids, bile acids, certain drugs
4) disease states

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Is echinocyte shape in RBC reversible?

yes

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erythrocyte functions

1) transport of oxygen
2) transport of carbon dioxide
3) buffering of H+ ions

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blood oxygen content is dependent on:

1) Hb content
2) pO2
3) Hb oxygen affinity (P50)

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What is the advantage of releasing O2 to tissues at a higher pO2? (Hb is unloading sooner)

creates a greater gradient for O2 delivery to the tissues

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What is the DISadvantage of releasing O2 to tissues at a higher pO2? (Hb is unloading sooner)

won’t be able to fully load the oxygen in the lungs and some of the animal’s Hb won’t even get used

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Increased 2,3 DPG –> Hb’s affinity for O2

decreases. Hb releases O2 sooner

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How does 2,3 DPG, temperature, CO2, and H+ effect Hb affinity for O2?

If any of them increase, Hb’s affinity for O2 decreases

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How do anemic dogs compensate for low Hb?

have higher 2,3-DPG lvls

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products of oxidative metabolism at the tissues?

CO2 and acids

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Where is binding of O2 to Hb maximized and minimized?

Maximized at the lungs, minimized at the tissues

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P50 represents

oxygen affinity. High p50 means lower O2 affinity

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Why do smaller animals have higher p50 than larger animals?

they have higher metabolic rates, therefore need more O2 released to tissues rapidly

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Why is there higher Hb affinity for O2 in fetal blood than maternal blood?

potentiates O2 delivery from mother to fetus. Fetus normally lives in a hypoxic environment, so it’s ok for their Hb to have a higher affinity for O2

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Where is majority of CO2 in body?

bicarbonate in the blood. Acts as a buffer and increases CO2 carrying capacity of blood

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Which binds more CO2: deoxyHb or oxyHb?

deoxyHb. Is triggered to bind CO2 once O2 is released

Where is carbonic anhydrase located? what does it do?

In erythrocytes. Catalyzes formation of bicarbonate from CO2 and H2O

major protein buffer in blood

which is stronger acid: deoxyHb or oxyHb?

OxyHb

what buffers organic acids produced by metabolism?

What are Heinz bodies?

oxidative denatured Hb

What is glucose ultimately converted to during the process of carbohydrate metabolism?

lactate, with production of ATP. 2,3-DPG is also produced in a side reaction.

What does pentose phosphate pathway generate? Why is it important?

NADPH. It keeps glutathione in a reduced state, which ultimately protects the RBC from oxidative injury

What will glutathione do if its oxidized?

become GSSG by reduction of H2O2

fx of reduced glutathione (GSH)?

free radical scavenger, electron donor for reductive enzyme reactions

What reduces GSSG back to GSH?

NADPH-dependent glutathione reductase

how does selenium act as an antioxidant?

It is incorporated into protective enzymes

how does catalase act as antioxidant?

degrades H2O2

how does ascorbate act as antioxidant?

donates electrons

how does vitamin E act as antioxidant?

membrane free radical scavenger

catalase reaction

H2O2 --> H2O + O2

What happens to H+ released from deoxyHb with CO2?

Combines with HCO3- to form H2CO3, which reversibly forms CO2 and H2O

How does pH change when Hb binds CO2?

only slightly lowers. Hb allows for transport of CO2 with only a slight change in pH

Describe composition and orientation of erythrocyte membrane lipids

phospholipid bilayer with hydrophobic hydrocarbon chains of fatty acids directed to the center of the bilayer. Unesterified cholesterol intercalated with FA chains. Glycolipids in the outer layer containing blood group antigens

Integral vs. skeletal membrane proteins on erythrocytes

integral memb. proteins are transmembrane glycoproteins that include receptors, transport proteins, and erythrocyte antigens. Skeletal memb. proteins form a lattice-like arrangement on inner surface of membrane that allow for a fluid lipid bilayer

where are blood group antigens produced? What are they composed of and why are they important?

erythroid cells. Composed mainly of carbs. important for animal ID and parentage testing. Most blood group antigens are the same across members of a species

clinically significant blood group antigens in horses

A and Q factors

clinically significant blood group antigens in dogs

DEA (dog erythrocyte antigen), and Dal (lacking in some Dalmations)

clinically significant blood group Ag in cats

AB group, Mik group

what are natural antibodies?

antibodies present BEFORE you give a transfusion. Most likely arise from carbs present on gut flora seen by the immune system, however they have never had exposure to the foreign RBC!

Erythrocyte method of metabolism

in absence of ribosomes, mitochondria, and ER, they utilize glucose in glycolysis and pentose phosphate pathway for energy.

Does DPG cycle generate net ATP gain?

What are RBC's energy requirements?

1) maintain Na and K concentrations 2) maintain shape and deformability 3) maintain 2,3-DPG concentrations 4) MetHb reduction 5) pentose phosphate pathway to protect against oxidant injury

oxidant damgae to Hb/enzymes/membrane unsaturated lipids can result in:

MetHb, heinz bodies, increased phagocytosis, intravascular hemolysis

difference between MetHb and Hb

MetHb has Fe in +3 state instead of +2 state, so it can't bind O2. This is a natural product of neutrophil activation

What converts MetHb back to normal Hb?

Cb5R. FAD is a cofactor for this process

What is majority of Fe in the body used for? **

RBC production. Majority of the body's iron is located in the RBCs ***

where is transferring produced?

liver

Where does majority of recycled Fe come from?

Macrophages, which break down old RBCs

True or False: Fe is highly conserved in the body

True

What brings Fe to developing RBCs?

transferrin

What stores Fe absorbed from the intestine?

interocytes. Stores Fe as ferritin

Fe+3 =

ferric iron

Fe+2 =

ferrous iron

What solubilizes Fe from food in the stomach?

HCl. Mucin helps keep it solubilized

2 mechanisms to absorb Fe into a RBC

1) Fe is reduced, then transported into cell via DcytB and divalent transporter 2) Heme carrier protein takes heme molecule in with bound Fe. Heme oxidase then breaks down and releases Fe into the cell

What converts Fe+2 to Fe+3?

hephaestin

what transports Fe out of RBC?

ferroportin

Why is too much Fe in blood bad?

Can be toxic and act as a free catalyst

If there is too much Fe entering a RBC, how is this compensated for?

Fe is stored as ferritin (a protein shell filled with Fe+3). This protects cell from damage

hepcidin fx

Inhibits ferroportin from depositing Fe into the body from the RBC. Increases when there is too much Fe in the body. Cell with excess Fe will then slough in the GI tract

inflammation --> iron absorption

decreases

increased erythropoiesis --> hepcidin release

decreased. Erythropoiesis requires more Fe to be available

Can hepcidin be increased even if Fe is low?

Yes.

Total iron binding capacity is a measure of:

transferrin concentration

Almost all Fe is bound to:

transferrin

Which binds Fe better: diferric or monoferric transferrin?

diferric. It can also deliver Fe to the body more efficiently

Majority of plasma iron is utilized for:

Hb synthesis. It mostly comes from macrophage release

where is heme formed?

inside mitochondria of RBC

Where is Hb formed?

in cytoplasm of RBC (heme leaves mitochondria and combines with globin)

Do reticulocytes have mitochondria?

Yes

What does hepsidin control?

How much Fe is present in the whole body. Master regulator of Fe homeostasis

apoferritin fx

intracellular Fe storing protein

TfR =

transferrin receptor. Carrier protein for transferrin that imports Fe into the cell

When is TfR expression promoted?

under conditions of low Fe content inside the cells

ceruplasmin fx

copper containing plasma protein that converts Fe from +2 to +3 state. (+3 state binds to transferrin)

Increased hepcidin --> Fe absorption

inhibited

hemosiderin

aggregates of protein and iron in lysosomes in a macrophage

increased intracellular Fe concentration --> apoferritin synthesis

increases

3 mechs of transporting Fe into the cytoplasm

1) DMT1 (used by duodenal enterocytes) 2) phagocytized erythrocytes (used by macrophages) 3) transferrin endocytosis (used by RBCs and other cells)

1 Hb binds ___ O2 molecules?

1st step in heme synthesis

formation of ALA. Occurs in the mitochondria

last step of heme synthesis

insertion of Fe into the heme group. Occurs in the mitochondria

Synthesis of globin monomers is promoted by:

increased free heme

increased free heme --> iron uptake by erythroid cells

inhibits

RBC lifespan in large vs. small animals

longer in large animals. Slower metabolism doesn't acquire as much damage to RBCs as quickly

Eryptosis

apoptosis in anucleated cells

band 3

an anion transporter that clusters to form a senescent antigen in old RBCs and mark them for destruction by macrophages

Signs of an aging RBC

1) altered phospholipids (increased surface PS) 2) altered carbs 3) altered proteins (partially degraded band 3)

High lvl of CO in the body indicates:

high lvl of RBC destruction

Where/how is CO produced in the body?

Inside macrophage when heme is broken down into biliverdin

biliverdin reductase

converts biliverdin to bilirubin

physiologic anemia

normal dropoff in Hb lvl post-partum. Animal can become anemic and Fe deficient

why does erythropoietin decrease post-partum?

at birth there are high red cells, oxygen, and 2,3-DPG due to recent transfusion of cord blood. Therefore, additional RBCs are not needed. (this short-lived however with increasing growth)

lifespan of adult vs. fetal RBCs

adult RBCs have longer lifespan