Martin Auer (100571.2073 at compuserve.com) wrote:
: Please help. I'm writing a book in which an alcoholic appears. Now I need
: to know what exactly happens in the body when a person drinks alcohol.
: What is the chemistry of it? Why is it addictive?
This is from "Alcoholism--the Biochemical Connection" by Joan
Discoveries about the way alcohol is processed in the body
have provided further evidence of a genetic link. For example,
Harvard scientists (L. Tunglai et al. 1977) recently came upon a
previously unknown liver enzyme responsible for metabolizing
alcohol. This enzyme, alcohol dehydrogenase II (II ADH), can
process or oxidize alcohol up to 40 percent more efficiently than
the liver enzymes most of us have. People who have this enzyme--
and most of us do not--have an inborn ability to drink very large
amounts of alcohol without becoming intoxicated. These are the
folks who can drink many of us under the table without getting
the least bit tipsy and or feeling hung over the next morning.
Researchers have also discovered that the absence of a
crucial liver enzyme accounts for the fact that very few
Orientals become alcoholics. In fact, many Asians get sick
whenever they drink. Their pulses race and they feel dizzy and
nauseated. The explanation for this peculiar reaction is the fact
that many Orientals have only one liver enzyme that processes
alcohol, rather than the two found in people from other parts of
the world. About half the Oriental population is missing this
second crucial enzyme.
Alcoholics and nonalcoholics process alcohol differently.
When alcohol reaches the liver, it is changed into acetaldehyde,
a harmful byproduct of alcohol metabolism that can damage liver
cells. Normally, the liver rapidly transforms the harmful
acetaldehyde into a neutral substance called acetic acid or
acetate. The acetic acid is then converted into carbon dioxide
and water. We expel the carbon dioxide through respiration and
the water through urination.
Until recently, it was believed that the liver always
handles alcohol in the same way. But new research shows that a
different scenario occurs among certain alcoholics and children
of alcoholics with no drinking experience. Their livers change
alcohol into acetaldehyde at twice the normal rate, while the
subsequent conversion of acetaldehyde into acetic acid is
abnormally slow and takes twice as long as usual. The
accumulation of acetaldehyde damages liver cells, which become
abnormally large as they strive to get rid of the accumulated
acetaldehyde. This damage affects the liver's ability to absorb
and utilize the nutrients needed for good health. To make matters
worse, excess acetaldehyde escapes the liver and travels through
the bloodstream to the heart, where it can be very damaging (it
interferes with the protein synthesis of the heart muscle). It
also reaches the brain, where it blocks proper neurotransmitter
action in creating normal feelings, behavior, and memory. The
unused natural neurotransmitters begin to build up and combine
with the acetaldehyde to form potent psychoactive compounds
called tetrahydroisoquinolines (THIQs), which are remarkable
similar to opiates. THIQs fit in the same receptor sites in the
brain as natural pain killing chemicals called endorphins and
such narcotics as morphine and heroin.
The Chemistry of Addiction
Two decades ago, Texas researcher Virginia Davis noticed
during autopsies of skid row alcoholics that their brains
contained an opiate that she first mistook for heroin. This was
puzzling because these indigents did not have the money needed to
support such an expensive drug habit. The heroin like substance
turned out to be THIQs that had been manufactured inside their
brains when acetaldehyde from the breakdown of alcohol had
combined with natural neurotransmitters. Davis's data support the
concept of alcoholism as a true addiction stemming from specific
biochemical events leading to the formation of an addictive
substance similar to opiates such as heroin.
We now know that in heavy drinkers, THIQs displace
endorphins and bind with the opiate receptors in the brain. In
doing so, they signal the brain to stop producing endorphins. As
the natural endorphin supply declines, more and more alcohol is
needed to produce more THIQs to replace the natural endorphins
and bind with opiate receptors to create feelings of well-being.
At the University of Texas, researcher Kenneth Blum, M.D.,
found that restoring these natural endorphins and
neurotransmitters destroyed or depleted by alcohol will reduce
cravings for alcohol and restore normal moods.
Some pertinent findings emerged from a study of the
reactions to alcohol among two groups of college students. One
group was composed of students who had a family history of
alcoholism; those in the second group had no alcoholism in their
backgrounds. After four drinks, the students from alcoholic
families produced much higher levels of acetaldehyde, and they
could perform a variety of mental and physical tests better under
the influence of four drinks than when they had not been
drinking. The students with no family history of alcoholism
reported feeling moderately intoxicated and showed impaired
physical dexterity, reflexes, mental ability after four drinks.