PERFORMANCE ENHANCERS WORK
BRIEF LESSON ABOUT DRUG TARGETS
All drugs have their own ‘mechanism of action’ – or way in which they
work. Most drugs' act at specific target called receptors. These specialized
proteins are located on cell membranes or inside cells in your body. To
visualize this concept, picture an outlet, like the one on a wall. Now
picture several of these outlets – or receptors – on the cells in your
body. These receptors act as switches that can either trigger or block
biological activity when stimulated/occupied. Drugs, and natural chemicals
in the body occupy, bind, or plug into the outlets to cause varying effects.
of a receptor – the adrenergic receptor – is shown to the left in Figure
1. The endogenous or natural chemical, norepinephrine, binds to its
receptor on a cell membrane, triggering a series of biochemical reactions
and cellular “work”. Throughout this presentation, you will hear about
each drug’s mechanism of action, and the receptors with which it interacts.
is a drug or other chemical that can bind to a receptor to produce a physiologic
reaction typical of a naturally occurring substance. Ephedrine can act
as an agonist of norepinephrine at adrenergic receptors.
is chemical substance or drug that interferes with the physiological action
of another, especially by binding and blocking its receptor.
STIMULANTS (EPHEDRINE AS EXAMPLE)
are used generally by athletes to stay alert, reduce fatigue, and maintain
aggressiveness. These drugs make the heart beat faster, open up lung passages
to make breathing easier, and help the brain focus better.
is the active compound in the plant called Ephedra or Ma
Huang. It is an alkaloid because it contains a nitrogen atom (see
blue atom in Figure 2).
A less potent version of ephedrine found in the Ephedra plant is pseudoephedrine,
which is contained in many popular decongestant cold remedies. Ephedrine
is banned from the competitive arena by the IOC, the IAAF, the USOC, the
information about alkaloids found in plants go to www.thepepproject.net
and click on Module 5.
HOW DOES EPHEDRINE WORK?
Ephedrine acts at the norepinephrine synapse, the connection between a neuron that releases norepinephrine and a neighboring cell.
is stored in vesicles in the terminal of a neuron (shown in Figure
3). Normally norepinephrine (also called noradrenaline) is released
in small quantities from the vesicles into the synaptic space. Then it
binds to adrenergic receptors on the receiving cell, and depending on
what type of receiving cell is present, e.g., a neuron or a cardiac cell,
a specific response is produced. Neurons might fire, or a cardiac cell
might fire to increase the heart rate.
principal mechanism of action, like that of amphetamine, is to cause more
norepinephrine to be released from its storage vesicles in the terminal
of neurons (Figure 4).
This increases the amount of norepineprhine in the synaptic space compared
to normal conditions. More norepinephrine binds to adrenergic receptors,
resulting in relaxation of the bronchioles, increased heart rate and blood
pressure, and a generally increased state of arousal. These effects are
sometimes called an “adrenaline rush”. Ephedrine can also bind to adrenergic
receptors to mimic the actions of norepinephrine.
are hormones or chemical substances derived from cholesterol. The human
body produces several kinds of steroid hormones. Of the ‘sex steroids’,
males produce mainly testosterone. Females produce mainly estrogen and
has both anabolic and androgenic effects. The ability of testosterone
to stimulate muscle and bone and cells to make more protein is called
the anabolic effect. The ability of testosterone to enhance male reproductive
and secondary sex characteristics (testicle development, hair growth,
deepening of the voice) is called the androgenic effect.
Anabolic steroids are synthetic analogs of testosterone. All anabolic
steroids have some degree of androgenic effects.
DO ANABOLIC STEROIDS WORK?
natural steroids, these synthetic steroids bind to steroid receptors in
many kinds of cells (see Figure
6). The steroid and its receptor are then carried to the nucleus where
they ‘instruct’ the DNA to transcribe messenger RNA (mRNA). The mRNA then
delivers its message to the ribosomes in the cytoplasm causing a an increase
protein synthesis. In muscle cells, this causes muscle growth. In bone
cells, this increases bone size.
learn more about how steroids work, go to www.thepepproject.net
and click on Module 6.
BLOOD BOOSTERS: EPO
or EPO, is a naturally occurring hormone produced in the kidneys. Specific
“sensors” in the kidneys monitor the oxygen (O2) content in the blood
(arterial side). If the amount of oxygen drops below a certain level,
EPO is released into the bloodstream. It then binds to specific EPO receptors
on the surface of cells in the bone marrow resulting in the production
of more erythrocytes (red blood cells). An increased number of red blood
cells carries an increased amount of oxygen to all cells in the body.
BLOOD BOOSTERS — EPOGEN®
Epogen® (Epoetin alfa) is a genetically engineered version of the natural hormone erythropoietin (EPO) found in the body. This synthetic version of EPO is used to treat anemia associated diseases such as diabetes and kidney disease. However, athletes use synthetic EPO to enhance their performance.
works the same way as natural EPO. When administered intravenously, it
travels to the bone marrow where it interacts with EPO receptors to stimulate
the production of red blood cells from bone marrow stem cells. The increase
in the number of red blood cells delivers more oxygen to all cells in
the body, especially muscle cells.
DO ATHLETES TAKE EPO?
get an extra edge if they are able to get more oxygen to their muscles.
By taking synthetic EPO, athletes can boost their red blood cell count
and are able to supply their muscles with oxygen for a longer amount of
time. Imagine oxygen as the fuel necessary to make the muscles work most
effectively--EPO essentially gives the athlete more fuel for their muscles.
This leads to increased performance and an unfair advantage over competitors.
athletes who use EPO can increase their the oxygen carrying capacity of
their red blood cells by as much as 7 to 10 percent!