Prostaglandin PGF2a
by Bryan Haycock
Where does it come from? How does it work? Taking a closer look at
this up and coming weapon in the bodybuilders arsenal
In January 1999, Mesomorphosis revealed a little known strategy being
used by several elite European athletes to boost size and strength.
What was this secret weapon? The prostaglandin PGF2 of course. It is
purported to increase muscle mass wherever you inject it, as well as
reduce body fat by increasing body temperature. This has caused quite
a stir within the bodybuilding community. Gym rats all over the globe
are already scampering to get their hands on this unique bodybuilding
tool. No doubt you will soon see other magazines jumping on the
bandwagon in order not to miss out on what Mesomorphosis has started.
Mesomorphosis believes that the day of bodybuilders blindly following
the advice of others based on hearsay is gone. For this reason,
bodybuilders must not only be abreast of what tools are available to
them in there quest for muscle growth, but also be educated about the
science behind these sometimes exotic compounds. Hereafter we will
take a closer look at prostaglandins and their role in muscle growth.
It is only after we gain knowledge that we can effectively put to use
those tools available to us.
Prostaglandins and their Discovery
Prostaglandins are part of a class of substances called eicosanoids.
Eicosanoids are a group of substances derived from fatty acids and
include prostaglandins, thromboxanes, and leukotrienes, all of which
are formed from precursor fatty acids by the incorporation of oxygen
atoms into the fatty acid chains. This reaction is called oxygenation
and is carried out by cyclo-oxygenase enzymes. Prostaglandins and
their metabolites have been found in virtually every tissue in the
body.
The discovery of prostaglandins and determination of their structure
began in 1930, when Raphael Kurzrok and Charles Lieb, both new York
gynecologists, observed that human seminal fluid stimulates
contraction of isolated uterine muscle. A few years later in Sweden,
Ulf von Euler confirmed this report and noted that human seminal fluid
also produces contraction in intestinal smooth muscle and lowers blood
pressure when injected into the blood stream. It was Von Euler who
came up with the name prostaglandin for this mysterious substance. The
name prostaglandin seemed appropriate because he thought it originated
in the prostate gland. Today, we know that prostaglandin production is
not limited to the prostate, in fact, there is virtually no soft
tissue in the body that doesn’t produce them. The name, however, has
stuck with us through the years. If Von Euler had known his name for
prostaglandins would still be with us into the next millennia, I’m
sure he would have chosen to name them "Von Eulers" or "UVEs" instead
of prostaglandins. By 1960, several specific prostaglandins had been
isolated in pure crystalline form and their structures determined.
Because our concern with prostaglandins involves primarily PGF2a, and
perhaps PGE2, we will not go into detail about the myriad of other
prostaglandins. Just know that prostaglandins are abbreviated "PG".
The additional letter and numerical script indicate the type and
series. The various types differ in the functional group present in
the five-membered ring.
While scientists were studying the structure of these new compounds,
other research was being done to determine their role in human
physiology and their potential as drugs. Initially these compounds
were extremely expensive to synthesize and/or isolate in sufficient
quantities for research. In 1969, the price of prostaglandins dropped
dramatically with the discovery that the gorgonian sea whip, or sea
fan, is a rich source of prostaglandin-like materials. Now however,
there is no need to rely on natural sources because chemists have
developed highly effective laboratory methods for the synthesis of
almost any prostaglandin or prostaglandin analog.
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Endogenous production from Arachidonic Acid
Prostaglandins (PGs) are not stored in the tissues of your body. PGs
are produced in response to some physiological trigger. The starting
material for PG synthesis are unsaturated fatty acids that have 20
carbon structures. The fatty acid that is used to make PGF2a is
arachidonic acid.
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Functions of prostaglandins in the body
Prostaglandins are classified as autocrine (effecting the same cell
that produced it), as well as paracrine (effecting adjacent cells),
regulators. They do not really fit into the category of hormones, nor
are they neurotransmitters, instead they are simply considered as a
corollary of the endocrine system.
The following are some of the regulatory functions of prostaglandins
in various organs and systems of the body:
Inflammation & Pain. PGs promote many aspects of the inflammatory
response. They are involved in the sensation of pain associated with
inflammation and vasoconstriction and/or dilation, and the development
of fever. PGs, when injected directly into the hypothalamus, induce
fever. Anecdotally, the use of PGF2a also induces a rise in body
temperature presumably by interacting with the hypothalamus as well.
Reproductive systems. PGs may play a role in ovulation and corpus
luteum function in the ovaries and in contraction of the uterus.
Excessive PG production may be involved in premature labor,
endometriosis, dysmenorrhea (menstrual cramps), and other
gynecological disorders. PGs are often given to induce labor.
Gastrointestinal tract. The stomach and intestine produce PGs. PGs are
believed to inhibit gastric secretions and influence gastric motility
as well as fluid absorption. Drugs such as
aspirin that inhibit
prostaglandin production can lead to overproduction of gastric
secretion. This predisposes the person to gastric ulcers.
Respiratory System. PGs can cause vasoconstriction as well as
vasodilation of blood vessels within the lungs, depending on which PGs
are being produced. PGs also cause both dilation and constriction of
bronchial smooth muscle. PGs as well as other eicosanoids may play a
role in asthma.
Blood vessels. Some PGs are vasoconstrictors, others are vasodilators.
The overall effect is determined by which PG is present in greater
concentration.
Blood clotting. Thromboxanes, also a product of cyclo-oxygenase, are
produced by blood platelets. These eicosanoids promote platelet
aggregation and vasoconstriction. Prostacyclin, produced by vascular
endothelial cells, inhibits platelet aggregation and causes
vasodilation.
Kidneys. PGs are produced in the medulla of the kidneys and cause
vasodilation, resulting in increased renal blood flow and increased
excretion of water and electrolytes in the urine. In particular, high
potassium intake has been shown to selectively increase PGF2a
excretion in animals.
Protein synthesis. PGs are known to be regulators of protein synthesis
in skeletal muscle. PGE2 and PGF2a being involved in protein breakdown
and protein synthesis rates respectively. Stretch induced hypertrophy
of skeletal muscle is in part regulated by prostaglandins. More on the
role of PGs in protein synthesis in later sections.
Adipogenesis. PGF2a directly inhibits adipogenesis. You should not be
surprised to hear that yet another prostaglandin serves to induce
adipogenesis, namely PGJ2. PGJ2 derivatives function as activating
ligands for peroxisome proliferator-activated receptor (PPAR), a
nuclear hormone receptor that is central to fat cell proliferation.
PGF2 blocks adipogenesis through activation of mitogen-activated
protein kinase (the same kinase involved in
insulin action), resulting
in inhibitory phosphorylation of PPAR. Both mitogen-activated protein
kinase activation and PPAR phosphorylation are required for the anti-
adipogenic effects of PGF2. So you have PGs within the cell telling
the fat cell to divide while at the same time you have other PGs, such
as PGF2a, at the outside preventing it from taking place.
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Current uses of PGF2a
Humans PGF2a is not currently FDA approved for use in humans. Products
containing PGF2a should be considered hazardous to women and must be
handled with extreme care. PGF2a is readily absorbed through the skin
and may result in birth defects and/or instantaneous abortion.
Prostaglandins of use today in humans are of the "E" class and are
administered to women for abortion or to induce labor. Prostaglandins
are also used for impotence in men. In such case it (PGE1) is injected
directly into the penis.
Animals PGF2a has been tested in a wide range of animals from monkeys
to horses. In most cases the side effects are increased body
temperature, vomiting and diarrhea, bronchial constriction, confusion,
loss of coordination, tachycardia, and low blood pressure just to name
a few. PGF2a is nontoxic with a serum half life of only minutes.
PGF2a is currently used in animal husbandry to manage breeding. It is
used commonly as dinoprost in the form of a tromethamine salt. Upjohn
makes a version called Lutalyse® as a sterile solution for
subcutaneous and intramuscular injection. It’s purpose is to
synchronizing ovulation in cattle by sequential injection of several
hormones along with PGF2a. A hormone selected from the group
consisting of gonadotropin releasing hormone (GnRH), luteinizing
hormone (LH), or human chorionic gonadotropin (hCG) is administered to
an open cow during an estrous cycle in order to stimulate follicle
development. PGF2a is then administered to initiate corpus luteum
regression about five to eight days after administration of the GnRH,
LH or hCG. A second dose of GnRH, LH or hCG is then administered
concomitantly with the PGF2a injection or up to about three days after
the PGF2a injection. This second dose of hormone functions to
stimulate the ovulation of a dominant follicle and the cow is then
breed within one day of the administration of the second dose of
hormone.
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The Role of PGF2a in Muscle Growth
After that brief introduction into prostaglandins, we can now begin to
discuss more specifically the role of prostaglandins in muscle growth.
In a nutshell, mechanical stimulation (i.e. intermittent stretch)
results in the production and efflux of two prostaglandins, PGE2 and
PGF2a. PGE2 increases protein degradation where as PGF2a increases
protein synthesis. Muscle hypertrophy is usually achieved by an
increase in protein synthesis as well as a proportionately smaller
increase in degradation. The simultaneous release of both PGE2 and
PGF2a creates this condition.
It is well known that mechanical stretch, without any electrical
activity, is sufficient to induce muscle hypertrophy. Recent studies
have shown that the mechanism by which mechanical stretch leads to
prostaglandin production and ultimately muscle growth, involves G
proteins embedded in the cell membrane. These G proteins increase the
amount of cyclo-oxygenase, the enzyme responsible for making
prostaglandins from arachidonic acid. Skeletal muscle cyclooxygenase
generates PGE2 and PGF2 alpha at a ratio approximately equal to one.
The exact mechanism by which PGF2a increases protein synthesis is not
entirely clear. That’s just a spineless way of saying, "I don’t know
the exact answer to that!" We are free to speculate though. It may
involve short phase protein synthesis and/or long phase protein
synthesis.
2 phases of protein synthesis Modulation
Modulation of protein synthesis rates occurs at two levels, the short
phase and the long phase. The short phase alteration in protein
synthesis rates occurs by altering the activity of existing ribosomes
and/or eukaryotic initiation factors (eIFs). This happens within
minutes of the appropriate physiological trigger. The long phase
modulation of protein synthesis happens by way of increasing the
number of myonuclei. This mechanism involves hormones and growth
factors such as HGH and IGF-1 bringing about the activation of
myogenic stem cells. This can take several days to effect protein
synthesis rates. This is a simplified view but for our purposes it is
sufficient.
The role of PGF2a in short phase protein synthesis in muscle tissue is
speculative at best. In non-muscle tissue, prostaglandins effect
calcium fluxes, plasma membrane ionic channel activities, and cyclic
nucleotide levels. All of which are important regulators of protein
synthesis rates in muscle. PGF2a has been shown to interact with the
S6 small ribosomal subunit, increasing its potential to form the
ribosomal initiation complex with the large subunits. It is also
plausible that PGF2a may effect the activity of eIFs.
Initiation of translation (the binding of mRNA to the ribosomal pre-
initiation complex) requires group 4 eukaryotic initiation factors
(eIFs). These initiation factors interact with the mRNA in such a way
that makes translation (the construction of new proteins from the mRNA
strand) possible. Two eIFs, called eIF4A and eIF4B, act in concert to
unwind the mRNA strand. Another one called eIF4E binds to what is
called the "cap region" and is important for controlling which mRNA
strands are translated and also for stabilization of the mRNA strand.
Finally, eIF4G is a large polypeptide that acts as a scaffold or
framework around which all of these initiation factors and the mRNA
and ribosome can be kept in place and proper orientation for
translation. There is yet no direct evidence to confirm that PGF2a
works through this mechanism however.
Long term modulation of protein synthesis involves the activation of
myogenic stem cells or satellite cells. If you recall, when a muscle
is stretched it not only produces PGF2a, but also PGE2. PGE2 is a
potent inducer of satellite cell proliferation and fusion. This is how
existing muscle cells increase the number of nuclei they contain. This
is important because in order for a muscle to grow rapidly, it must
produce more mRNA. This is done in the nucleus of the muscle cell. The
more nuclei you have, the more mRNA you can produce. Within the cell,
prostaglandins may also be involved in regulating the number of
ribosomes. This could have long term implications on growth and
development as well as stretch induced hypertrophy.
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The role of other hormones, drugs and diet in the action of PGs.
Because prostaglandins are signaling molecules that get their message
across through multi step signal transduction pathways, they are
susceptible to modulation by several chemical, hormonal, and dietary
factors. I will do my best to shed some light on the subject without
bogging you down with meaningless terms and jargon. It is well to
remember that the action and interaction of prostaglandins in the
human body is complex.
Cortisol
Cortisol effects the production of prostaglandins in muscle tissue by
at least two mechanisms. First, cortisol by way of lipocortins,
inhibits the action of phospholipase A2. Phospholipase is necessary in
order to make arachidonic acid available for PGF2a production.
Cortisol also inhibits the production of cyclo-oxygenase mRNA content
within cells. As mentioned earlier, cyclo-oxygenase is the enzyme that
converts arachidonic acid into prostaglandins. So cortisol inhibits
muscle growth by preventing the production of PGF2a in response to
training (mechanical stimulation) and eating (insulin action).
Insulin
As eluded to above, insulin stimulated protein synthesis is linked to
the production of phospholipases which lead to increased availability
of arachidonic acid. This is a two edged sword. Increased availability
of arachidonic acid can increase the amount of PGF2a thereby
increasing protein synthesis. On the other hand, arachidonic aid
directly suppresses GLUT4 production which is the chief glucose
transporter in skeletal muscle. High levels of arachidonic acid can
reduce glucose transport by up to 50%. It could be that insulin action
is more dependant on the cAMP antagonist, cyclic PIP
(prostaglandylinositol cyclic phosphate), a proposed second messenger
for insulin and alpha-adrenoceptor action, than on PGF2a. PGE2 however
is a different story. Prostaglandin E, myo-inositol and one phosphate
are components of cyclic PIP. So increased production of PGE2 may
increase insulin mediated glucose transport through this mechanism.
Taking this into consideration, exogenous PGF2a should not be
considered to replace insulin.
Dietary Fatty Acids
Dietary fatty acids significantly effects prostaglandin production.
Diets high in omega-3 fatty acids (fish oil, flax oil) decrease
prostaglandin production. Diets high in omega-6 fatty acids (corn oil)
increase prostaglandin production. Once again you have pros and cons
with trying to manipulate PGF2a production with your diet. By
increasing omega-3s, you get lower levels of PGF2a and probably a less
intense stimulus of protein synthesis immediately after you workout.
On the other hand by increasing omega-3s you reduce inflamation, pain,
increase GLUT4 content, and a whole host of other factors related to
cardiac risk. I don’t think its as clear cut as Dr. Sears (Zone Diet)
would have you believe. Trying to manipulate the diet to control
prostaglandin kinetics is fraught with complexity making black and
white statements difficult to support.
NSAIDs
NSAIDs are non-steroidal anti-inflammatory drugs. An example of such
drugs are aspirin,
ibuprofen (Motrin),
naproxen sodium (Anaprox,
Alleve). There are several more but these are the most common to
consumers. NSAIDs work by inhibiting the activity of cyclooxygenase.
By blocking cyclooxygenase you block prostaglandin production. These
drugs have been shown to improve nitrogen balance under conditions of
severe physical stress such as after surgery. The effect is abolished
when PGE2 is infused linking PGE2 production with the catabolic effect
of stress. In the case of PGF2a, the use of NSAIDs also blocks its
production in that PGE2 and PGF2a are normally produced in a 1:1 ratio
from the same precursor. Using NSAIDS while using exogenous PGF2a may
improve the anabolic effect by reducing PGE2 in the presents of
elevated PGF2a shifting the ratio towards anabolism.
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PGF2a + IGF-1: The ultimate cocktail for localized muscle growth?!
Say good by to lagging body parts forever. It is a special time to be
a bodybuilder. With the advent of PGF2a as a localized anabolic agent
along with the newly available rhIGF-1 which has also been shown to
build muscle where you want it, the future for genetically challenged
bodybuilders looks bright indeed. A brief refresher course on locally
injected IGF-1. Non-exercised muscle, when injection with 0.9 - 1.9
micrograms/kg/day of rhIGF-1 was shown to mimic the effects of
physically loading the muscle. Much the same effect PGF2a but by
different mechanisms. With local IGF-1 injections there is an increase
in protein content, cross sectional area and DNA content. The increase
in muscle DNA is presumed to be a result of increased proliferation
and differentiation of satellite cells which donate their nuclei upon
fusion with damaged or hypertrophying muscle cells. Take note that the
quantities of IGF-1 needed are extremely small, much smaller than
studies that have shown relatively poor results from administering
IGF-1 systemically which range from 1.0 to 6.9 milligrams/kg/day.
Now add PGF2a to the mix and whalla! You can virtually mimic the
mechanical stimulus of training without even picking up a weight. You
have PGF2a to accelerate short term protein synthesis by activating
ribosomes and/or eIFs and thereby translation, as well as IGF-1 to
activate satellite cells to bind and donate additional nuclei to boost
the amount of mRNA to be used by the ribosomes. Because the mechanism
of action is different, the two compounds should compliment each other
delivering results beyond what either one alone could produce.
Are these compounds going to replace traditional training? Not in the
near future. The use of site injectable drugs only reaches the surface
musculature. Deeper muscles are only stimulated to grow with
traditional training. For strength athletes, strength is dependant on
neuromuscular training which is not enhanced by simple muscle
hypertrophy without actual lifting in a coordinated fashion. Are these
compounds going to replace traditional anabolics? No. The reason is
basically the same as with training. Deeper muscle groups are only
reached by systemically administered anabolics that are carried
throughout the entire body. In addition, androgens are needed to
influence genetic expression in favor of whole body skeletal muscle
growth. Are these compounds going to change the face of bodybuilding?
It is very likely that they will, depending on their availability and
cost. I would hope that as competitors become educated about these
alternatives that we will no longer see implants in top level
competitors. It would also be nice to see people have an option when
it comes to pumping their muscles full of "stuff" in hopes that it
will improve their symmetry. No doubt the future will bring us even
more new and exciting drugs like non-steroidal androgens and compounds
that alter the expression of myostatin (GDF8). Once again, it is an
exciting time in the science of bodybuilding, perhaps now more than
any other time since the introduction of testosterone.
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