3. Plasma Proteins & Dysproteins

Plasma proteins are comprised of ________ of proteins. There are many protein ________ and ________.

hundreds; structures; functions

Where are the sites of plasma protein synthesis?

liver and lymphoid organs

Where is the major source of synthesis for most plasma proteins?

liver

Where is the synthesis of immunoglobulins?

lymphoid organs

What is plasma composed of?

water and protein

What are proteins composed of?

albumin, globulins, and fibrinogen

What is not present in serum?

fibrinogen

What happens when serum clots?

consumes platelets, fibrinogen, and various coagulation factors

What are the functions of plasma proteins?

T
C
A
R
I
H

• transport of nutrients, small hormones, waste, and drugs

• colloid osmotic effects

• acid-base

• regulatory proteins for cell production, inflammation

• immune defense

• hemostasis

What is the typical neonate total plasma protein concentration?

4-6 g/dL

What is the typical adult total plasma protein concentration?

6-8 g/dL

Neonates lack immunoglobulins until when?

colostrum ingestion and absorption

What happens with immunoglobulins as young animals are exposed to a wide variety of antigens?

continue to increase

What are the protein measurement methods?

P
B
F

• physical

• biochemical

• fractionation

What is an example of physical protein measurement methods?

refractometric

What is an example of biochemical protein measurement methods?

spectrophotometric

What is an example of fractionation protein measurement methods?

electrophoresis

What is measured in a microhematocrit tube?

packed cell volume (PCV) or Hct

What gives the buffy coat its appearance?

leukocytes and platelets

What affects plasma appearance?

I
L
H

• icterus index (yellow color)

• lipemia (chylomicrons/VLDL)

• hemolysis (free hemoglobin)

What does the microhematocrit tube allow determination of?

plasma protein and fibrinogen

True or false: You normally will not see a big buffy coat. If the animal has extremely high platelet count or WBC count, you can see a bigger buffy coat.

true

Where is the buffy coat found?

between the plasma and the PCV

a routinely performed method in veterinary medicine that is a quick screen of the total plasma protein that can also be used for urine specific gravity that is based upon the fluid’s refractive index

refractometric

What can cause erroneously increased plasma protein concentrations?

H
L
M

• hemolysis in the sample

• lipemia

• marked increases in nonprotein solids

Why does hemolysis in the sample cause increased plasma protein concentrations?

hemoglobin is not a plasma protein

Why does lipemia caused increased plasma protein concentrations?

interference with light transmission

What are reasons for a normal HCT with low total plasma protein?

G
P
L

• GI protein loss

• proteinuria

• liver disease

What are reasons for a normal HCT with normal total plasma protein?

nothing, this is normal

What are reasons for a normal HCT with high total plasma protein?

I
D

• increased globulin synthesis

• dehydration masked anemia

What are reasons for a high HCT with low total plasma protein?

protein loss combined with relative or absolute erythrocytosis

What are reasons for a high HCT with normal total plasma protein?

S
A
D

• splenic contraction

• absolute erythrocytosis

• dehydration masked hypoproteinemia

What are reasons for a high HCT with high total plasma protein?

dehydration

What are reasons for a low HCT with low total plasma protein?

S
O

• substantial ongoing or recent blood loss

• overhydration

What are reasons for a low HCT with normal total plasma protein?

I
D
C

• increased erythrocyte destruction

• decreased erythrocyte production

• chronic hemorrhage

What are reasons for a low HCT with high total plasma protein?

A
M

• anemia of inflammatory disease

• multiple myeloma or other lymphoproliferative disease

True or false: In the biochemical colorimetric method, when the reagent is added it typically results in a color change. Spectrophotometry is used to then measure the amount of absorbance and tells the amount present.

true

How are total protein and albumin concentrations in serum or plasma measured?

separately using 2 different spectrophotometric assays

How is total globulin concentration found?

it is calculated

How is total globulin concentration calculated?

by subtracting albumin concentration from total protein concentration

What is the formula for total globulin concentration?

total protein - albumin = total globulins

True or false: If the albumin is abnormal, you will get an abnormal globulin. For example, if the albumin is too high, the globulins will be too low.

true

How does fractionation of serum/plasma proteins work? What does this do?

separates by protein electrophoresis; gives various alpha, beta, and gamma globulin bands that stain the proteins for protein, carbohydrate, and lipids

In protein electrophoresis, the ________ charged proteins migrate to the ________ charge of the anion. The goal is to see how ________ they migrate.

negatively; positive; fast

What is it based off of? What does this mean?

charge density; more negative and small will travel fast

Which protein will migrate the farthest? Why?

albumin; basically the smallest protein and is very negative

What stain is used for serum protein electrophoresis?

coomassie blue

When would a serum protein electrophoresis test be performed?

U
I

• unexplained hyperglobulinemia

• immunoglobulin deficiency is suspected

True or false: Serum protein electrophoresis abnormalities are seldom specific for a given disease.

true

single homogenous protein that has a small molecular weight of about 66 kDa that contains minimal carbohydrate

albumin

What is a very important role for albumin? Why?

osmotic pressure; albumin has several times more molecules compared to other proteins and since it is so small and everything else is so big, if it drops, it will change the osmolality and osmotic nature resulting in peripheral edema

What results in edema?

hypoalbuminemia

What are the transport functions of albumin?

O
C
M
C
P
T

• organic and inorganic substances

• cations (mostly Ca)

• metabolites

• certain hormones

• poorly soluble drugs

• toxic substances

What usually accompanies hypoalbuminemia?

low total Ca in the blood

Albumin is a ________ ________-phase protein.

negative acute

proteins with more than 25% change in serum concentrations in response to inflammatory cytokines (IL-1, TNFa, IL-6)

acute-phase proteins (APPs)

How can acute-phase proteins be categorized?

positive or negative

acute-phase protein with increasing serum concentration

positive

acute-phase protein with decreasing serum concentration

negative

What is a sensitive indicator of inflammation? When can this occur?

increased production of acute-phase proteins; prior to the development of an inflammatory leukogram

In what species is a measurement of acute-phase proteins especially helpful? Why?

cattle and manatees; often do not exhibit prominent leukogram changes in response to inflammation

In dogs, what are the major > 10 fold increase positive acute phase proteins?

SAA and C-reactive protein

In cats, what are the major > 10 fold increase positive acute phase proteins?

SAA

In horses, what are the major > 10 fold increase positive acute phase proteins?

SAA

In cows, what are the major > 10 fold increase positive acute phase proteins?

SAA and haptoglobin

In sheep, what are the major > 10 fold increase positive acute phase proteins?

SAA and haptoglobin

In goats, what are the major > 10 fold increase positive acute phase proteins?

SAA and haptoglobin

In pigs, what are the major > 10 fold increase positive acute phase proteins?

SAA

What is the major acute phase protein in all common domestic mammals?

serum amyloid A

family of apolipoproteins associated with high-density lipoproteins (HDLs)

serum amyloid A

In normal animals, in what concentrations is serum amyloid A present in?

very low

What is the major acute phase protein in dogs and humans?

C-reactive protein

How is C-reactive protein normally present?

in very low concentrations

What is the major acute phase protein in ruminants?

haptoglobin

In what region does haptoglobin typically migrate in?

a2-region

What percent CHO is haptoglobin?

20%

What are functions of haptoglobin?

P
P
A

• prevents initial loss of free Hb in urine

• protects against bacterial infections

• antioxidant activity

How is fibrinogen classified as?

coagulation factor 1

What is fibrinogen the precursor to in coagulation?

fibrin

What causes optimal platelet aggregation?

fibrinogen

Fibrinogen acts as ________ for inflammatory cells, fibroblasts, and endothelial cells when deposited in tissues.

scaffolding

Fibrinogen is a ________ ________-phase protein.

moderate acute

What does fibrinogen do most prominently in horses, cattle, and goats?

increases in inflammation

Do we mainly use electrophoresis for plasma or serum? Why?

plasma has fibrinogen, which will show up in the middle of the beta and gamma regions → those are the peaks to look for antibodies and the fibrinogen peak will make it harder to interpret

How do you estimate fibrinogen?

fibrinogen = total protein before - total protein after

When is fibrinogen increased?

A
D

• active inflammation (cattle, goats, and horses)

• dehydration (all plasma proteins)

When is fibrinogen decreased?

D
L
S

• disseminated intravascular coagulation (DIC) sometimes

• liver failure

• snake venoms

What is the problem with the heat precipitation estimation method when it comes to fibrinogen?

too insensitive to clearly detect low values

protein important for copper transport

ceruloplasmin

Ceruloplasmin has ________ activity that facilitates ________ ________ from tissue stores.

ferroxidase; iron mobilization

Ceruloplasmin is a plasma ________ and an __________ -protein.

antioxidant; a2

iron-binding metalloprotein

transferrin

What does transferrin correlate with?

total iron binding capacity (TIBC)

What is transferrin responsible for?

iron transport throughout the body

Transferrin is a ________ ________-phase protein.

negative acute

iron-containing protein that is primarily found inside cells

ferritin

What type of concentration does ferritin have in plasma?

low

What does plasma ferritin correlate with?

total body iron stores

What type of protein is ferritin? What might high values reflect?

acute-phase protein; inflammation

bind small molecular weight hormones, preventing them from being rapidly filtered by the kidney

hormone binding proteins