kinds of plasma protein
Effects of Protein Meals on the Urinary Excretion of Various Plasma Proteins in Healthy Subjects
Takuma Narita, Hiroji Kitazato, Jun Koshimura, Katsunori Suzuki, Masahiko Murata, Seiki Ito
Division of Geriatric Medicine, Akita University Hospital, Akita, Japan
Address of Author
Nephron 1999;81:398-405 (DOI: 10.1159/000045323)
Key Words
- Acute protein loading
- Urinary excretion, proteins
- Size selectivity
Abstract
To examine whether hemodynamic changes in response to acute protein loadings with different protein sources cause increases in urinary excretion of plasma proteins in healthy subjects, urinary excretions of various plasma proteins with various molecular radii and isoelectric points, namely albumin (Alb), IgG, IgG4, ceruloplasmin (CRL), and 
2-macroglobulin (A2), were measured in healthy subjects after ingestion of a beef meal or of a tuna fish meal. Significant increases in urinary excretions of the negatively charged IgG4 and CRL and of the neutrally charged IgG were found in parallel with enhanced creatinine clearances after each protein ingestion. These renal responses returned to basal levels 9 h after the test. This finding suggests that in healthy subjects, the increase in glomerular filtration rate after acute protein loading caused selective enhancement of urinary excretions of plasma proteins with a molecular radius of approximately 55 Å (the radius of IgG, IgG4, and CRL), irrespective of the charge barrier of the glomerulus. The increases in these three plasma proteins may be induced by leakage via the shunt pathway in the glomerulus, as proposed earlier (see text). In contrast, increases in urinary excretions of A2 and Alb were not found. The former finding may be explained by the possibility that A2 would not pass through this pathway, since the molecular radius of A2 (88 Å) is larger than that of IgG, although the latter finding may be partially explained by preferential renal tubular reabsorption of Alb.
1
The Blood
Chapter 11
The blood is the medium for
the transport of substances
around the body.
•The blood is composed of:
–Mostly water-plasma 54-58%
–Red blood cells (41-45%
–Everything else (WBC’s, plateletes,
proteins, etc) 1%
Packed cell
volume, or
hematocrit
Plasma = 55% of whole blood
“Buffy coat”
<1%
Platelets
White blood cells
Red blood cells =
45% of whole blood
Three types of cellular elements
in the blood are: erythrocytes,
leukocytes, and platelets.
• The plasma is the liquid part of the blood.
– About 99% of the cells are erythrocytes.
– The hematocrit is the percentage of total blood
occupied by erythrocytes. It averages 42% in
women and 45% in men.
– The plasma is 90% water.
• Let’s look at it first.
Plasma consists of water
and other substances.
• The plasma consists of water (90%)
which is a transport medium for all blood
borne substances, &
• Ions, gases, nutrients, hormones, and
plasma proteins (10%).
• The majority is plasma proteins (8%).
Plasma Proteins
• Plasma Proteins have numerous functions:
–Establish an osmotic gradient between the
blood and interstitial fluid. (osmotic pressure)
–Proteins buffer pH changes.
–Aid in the transport of many blood-borne
substances (hormones, etc.)
–Function in immunity as antibodies (some).
–Fibrinogen is a key factor in blood clotting.
2
The other main component of the
blood is red blood cells (RBCs) or
Erythrocytes = transport oxygen.
• They also transport carbon dioxide and hydrogen ions.
• The diameter of an erythrocyte is about 8 um.
• This cell lacks a nucleus, organelles, and ribosomes.
• It is mainly a package of hemoglobin molecules +
iron.
• Its flat, biconcave, disc shape is well-suited to carry
out its main function: carry Oxygen.
• The plasma membrane of the erythrocyte is flexible.
This allows it to slide through a capillary (which
averages 7 um).
Hemoglobin is a molecule
consisting of two parts.
• The globin is four, folded polypeptide chains.
• The heme (iron) part is non-protein. Each of its
four iron atoms is bound to one of the
polypeptides and can combine with one molecule
of oxygen gas.
• Hemoglobin can also combine with carbon
dioxide, hydrogen ions, carbon monoxide, and
nitric oxide.
• Hemoglobin can buffer pH by binding with
hydrogen ions.
Polypeptide chain
Polypeptide chain Polypeptide chain
Polypeptide chain
Heme groups
The bone marrow
produces erythrocytes.
• Erythrocytes lack a nucleus so cannot
reproduce.
• Erythropoiesis (erythrocyte production) is the
production of new red cells, replacing the wornout
cells in the circulation.
• The average life span of a RBC is 120 days.
• The number of RBC’s normally remains
constant.
• Cell production equals cell death.
Erythropoiesis is controlled
by erythropoietin.
• If oxygen delivery to the tissues is decreased, the
kidneys detect this and increase the output of
erythropoietin and erythropoiesis increases.
• This increases the number of RBC’s and the
oxygen-carrying capacity to the tissues.
• Once the oxygen delivery to the tissues and
kidneys is sufficient, the kidneys decrease their
output of erythropoietin.
• Erythropoietin can be produced in the lab.
Kidney
Reduced oxygencarrying
capacity
Increased oxygencarrying
capacity
Relieves
Erythrocytes
Developing
erythrocytes
in red bone
marrow
Erythropoietin
3
Anemia is a lower than normal oxygen
carrying capacity of the blood .
There are many kinds of anemia:
• Nutritional anemia (low iron in diet).
• Pernicious anemia (vitamin B-12 deficiency)
• Aplastic anemia (failure of the bone marrow to
make adequate numbers of RBC’s).
• Renal anemia (kidney disease).
• Hemorrhagic anemia ( loss of blood).
• Hemolytic anemia (rupture RBC’s).
• Sickle cell disease
Polycythemia is an excess
in circulating erythrocytes.
• It produces an elevated hematocrit.
• Primary polycythemia is caused by an
tumorlike condition in the bone marrow.
• Secondary polycythemia is an erythropoietininduced
adaptive mechanism to improve the
oxygen-carrying capacity in the blood.
• Other conditions can elevate the hematocrit,
such as dehydration.
Normal
(hematocrit
= 45%)
Anemia
(hematocrit
= 30%)
Polycythemia
(hematocrit
= 70%)
Dehydration
(hematocrit
= 70%)
= Plasma = Erythrocytes
One of the other main
constituents of the blood
is Leukocytes (WBC’s)
These form one of the body’s major means
of defense against foreign invasion.
Leukocytes (also called white
blood cells WBCs) are the mobile
units of the body’s immune system.
• Defend against the invasion of pathogens (bacteria
& viruses, they form anitbodies).
• They identify cancer cells.
• They remove the body’s litter (waste) by
phagocytosis.
• They can leave the circulation and go to the sites of
invasion and tissue damage. (parasites & allergies)
• There are five kinds of leukocytes.
The five kinds of leukocytes
fall into two main categories.
1. neutrophils
2. eosinophils
3. basophils
4. monocytes
5. lymphocytes.
4
The last component of the
blood to be discussed
here is the platelets.
Platelets allow blood to clot which prevent
uncontrolled bleeding.
This is called: hemostasis
Platelets (thrombocytes)
function in hemostasis.
• Platelets are cell fragments derived from
undifferentiated blood cells from the bone
marrow.
• They remain functional for about 10 days.
• The hormone thrombopoietin increases
the number of platelets. Their overall
production is not well understood.
Hemostasis prevents blood loss
from damaged blood vessels.
• The first two steps to stop escaping blood
from a vessel are:
–vascular spasm - This reduces blood flow
through a damaged vessel.
–platelet plugging - An aggregation of
platelets forms a plug.
• The platelet plug seals a break in a vessel.
The third step to block escaping
blood is clot formation.
• This reinforces the platelet plug and converts
the blood to a gel in the area of the vessel
damage.
• The ultimate step in clot formation is the
conversion of fibrinogen (large and soluble
plasma protein) into fibrin (thread-like
protein).
• Fibrin threads trap RBCs, forming a clot.
• This process involves the clotting cascade.
The clotting cascade is a series of
steps involving twelve clotting factors.
• The clotting factors serve as proteolytic
enzymes in a series of reactions, the
clotting sequence.
• One factor in the sequence is activated
which, in term, activates another factor
and so on.
• This sequence is called the clotting
cascade.
Platelet
factor 3
(PF3)
Platelet
aggregation
Secretes
Other factors in Enhances
clotting cascade
Prothrombin Thrombin
Activation
Stimulates
conversion
Fibrinogen
Fibrin
(loose
meshwork)
Factor XIII
Activates
Fibrin
(stabilized
meshwork)
5
Figure 11.14
Page 407
Vessel damage
Exposed collagen
Platelet
aggregation
Activation of
factor XII
(Hageman
factor)
Activation
of thrombin
Activation of
next thrombin
Formation of
fibrin meshwork
of clot
Seal
damaged vessel
PF3
Clotting
cascade
One of the most important
functions of the blood is to
carry oxygen to the tissues.
The other part of oxygen delivery is the
Respiratory System, our next topic of
discussion.
