5. Erythrocytes: Function and Normal/Abnormal Destruction

How much does hemoglobin increase the oxygen carrying capacity of blood?

about 70X that of plasma

What is the blood oxygen content?

H
P
H

• hemoglobin content

• pO2

• hemoglobin oxygen affinity (P50)

What is P50 of oxygen?

when hemoglobin is 50% saturated with oxygen

If there is a higher O2 affinity, what will happen with P50?

lower P50

If there is a lower O2 affinity, what will happen with P50?

higher P50

increases the carbon dioxide carrying capacity of blood by 17 fold

70% bicarbonate buffer

What do erythrocytes contain that transforms CO2 and water to H2CO3?

carbonic anhydrase enzyme

What percent of carbon dioxide is dissolved?

5%

What percent of carbamino groups are on hemoglobin?

25%

What binds 2X more the amount of CO2 than oxyhemoglobin?

deoxyhemoglobin

What promotes the release of O2 from oxyhemoglobin?

increased CO2 and H+ concentrations in tissues

What binds the increased amounts of H+ and CO2?

deoxyhemoglobin

What does H+ release combine with and form? What does that then form?

H+ combines with HCO3- forming H2CO3; reversibly forms CO2 and H2O

What is the major protein buffer in the blood?

hemoglobin

Which is a weaker acid: deoxyhemoglobin or oxyhemoglobin?

deoxyhemoglobin

Hemoglobin buffers the effects of _______ _______ and allows for the ________ transport of ________ ________. It also buffers ________ ________ produced by metabolism.

carbonic acid; isohydric; carbon dioxide; organic acids

Do erythrocytes have nuclei? What does this mean?

no; they cannot synthesize DNA or RNA

What else do erythrocytes lack? What does this mean?

R
M
E

• ribosomes

• mitochondria

• endoplasmic reticulum

no Kreb’s cycle, protein synthesis, or lipid synthesis

What is the main way that erythrocytes get their energy? What is another way?

90-95% glycolysis; 5-10% pentose phosphate pathway

How much ATP is generated in the diphosphoglycerate pathway?

no net ATP is generated

self-antigens

alloantigens (isoantigens)

Different antigens produced at one chromosomal locus involves how many allelic genes?

2 or more

Most blood group antigens are what?

carbohydrates (glycolipids and glycoproteins)

What are most blood group antigens produced by?

erythroid cells

What decisions do blood antigens affect?

blood donor decisions

True or false: Erythrocytes contain many antigens, but most are not shared by all animals in a species or do not stimulate a clinically significant immune response.

true

After a mismatched blood transfusion, what is expected to be present in plasma? Within how long?

antibodies; 3-5 days

What can identify the presence of antibodies not identified or predicted by blood typing?

blood crossmatching

What are the dog major blood group antigens?

DEA 1

What are the major blood group antigens in cats?

AB group, Mik antigen

What are the major blood group antigens in horses?

A & Q factors

antibodies to blood group antigens present in plasma without prior transfusion or pregnancy

natural antibodies

Natural antibodies are present but not clinically important in ________, but they are important in ________.

dogs; cats

B positive cats have naturally high amounts of what?

strong-acting anti-A antibodies in their plasma

A positive cats have naturally variable amounts of what?

weak-acting anti-B antibodies in plasma

In cats, which blood antigen group is there no commercial test available?

Mik group

What are types of oxidant injuries to erythrocytes that can be identified in either whole blood or stained blood films?

E
C
G
N
E
H
M

• exposure to low levels of oxidants (oxygen and nitrogen free radicals)

• certain drugs and compounds produce high levels of oxidants

• glutathione and antioxidant enzymes

• NADPH from the pentose phosphate pathway provides electrons for the reduction of oxidants

• enzymes with reactive sulfhydryl groups

• hemoglobin (methemoglobin and Heinz bodies)

• membranes (eccentrocytes, hemolysis, increased phagocytosis)

What are erythrocyte lifespan directly related to? What is it in domestic mammals?

body weight; 2-5 months

What occurs during cumulative oxidant injury?

E
M
B

• eryptosis (cell death like apoptosis)

• membrane damage with altered phospholipid and carbohydrates

• band 3 clustering froms a senescent antigen

How are aged erythrocytes removed from blood? Especially where? Essentially, what does not occur within systemic circulation?

by phagocytosis; in the spleen; no lysis

What recognizes damaged erythrocytes?

macrophage receptors

What are the scavenger receptors?

A
A
A

• altered phospholipids (increased surface phosphatidylserine (PS)

• altered carbohydrates (desialation of sialoglycoproteins)

• altered proteins (partially degraded band 3)

How does the antibody bind the erythrocyte in order to destroy it? How does it promote phagocytosis?

binds the senescent antigen; promotes it through Fc and C3b receptors