On Thu, 16 Nov 1995 skim at alliant.snu.ac.kr wrote:
> Dear Jo,
>> Thank you for your kind explanation about antioxidant properties of melatonin.
> It is very interisting to me. I have several questions about melatonin.
>> 1. Is physiological level of melatonin sufficient to exert its antioxidant
> action? I've heard that hormone level in blood is very low. Thus I have a
> doubt about physiological significance of antioxidant action of melatonin.
A little known fact about melatonin is that it accumulates
preferrentially in the nucleus of the cell. Concentrations
1,000 times greater have been found in the nucleus. For
a reference:"Distribution of melatonin in mammalian tissues:
The relative importance of nuclear versus cytosolic
localization" J. of PIneal Research 1993;15:59-69"
To determine whether physiological levels of melatonin offer
significant antioxidant protection, Reiter performed a
fascinating experiment. He subjected rodents to a
potent, free-radical generating carcinogen called "safrole"
during the daytime to one group of rats and during the
nighttime --- when melatonin levels are naturally high -- to
another group of rats. The rats who were given the carcinogen
at night (and thus had high natural levels of melatonin) suffered
significantly less damage to their DNA. For a reference:
"Both Physiological and pharmacological levels of melatonin
reduce DNA adduct formation induced by the carcinogen
safrole." Carcinogensis 1994; 15:215-218
>> 2. If one takes a melatonin supplement, is there any change in endogenous
> production of melatonin? Or is there any known mechanism of regulation of
> its production like other hormones?
SHort term administration of melatonin to humans (2 months) has
shown no decrease in endogenous melatonin production. HOwever,
taking melatonin at certain times of day can either phase-advance
or phase-delay one's own melatonin production.
It is not known whether or not long-term melatonin supplementation
will alter endogenous melatonin production in humans.
A recent rodent study, however, has determined that chronic
melatonin administration actualy *increases* the number of
melatonin receptors in the brain -- a paradoxical finding.
For a reference:"Effects of long-term administration of
melatonin and a putative antagonist on the ageing rat."
NeuroReport 6:785-788. 1995.
>> 3. Do you know any disease condition that is associated with
decreased level
> of melatonin? Vit. E deficiency has been proved to result in neurological
> abnormalities. How about melatonin?
There is a long list of diseases and conditions associated
with low melatonin levels including:
chronic pain
alcoholism
depression
late stage cancer
diabetes
Alzheimer's disease (virtually undectable levels)
aging in general
schizophrenia
PMS
autism
You will find the references for all of these conditions in
our book, Melatonin: Your Body's Natural WOnder Drug.
>> 4. Is there any site other than pineal gland that can produce melatonin?
Interestingly, melatonin is also produced in the gut, including
the appendix, and the retina.
>> 5. How about long-term toxicity of melatonin supplementation? or Is it possible
> that withdrawal of supplement does harm to people?
Melatonin has no known toxicity. In Holland 1400 women have
been taking 75 milligrams of melatonin each night for 4+ years
No significant side effects have been recorded.
(Melatonin, Cohen, Michael. SHeba Press 1995)
DOzens of other clinical trials have shown that melatonin has
no toxic effects. You'll find additional references in our book.
>> I hope not bothering you much.
> Thank you in advance for your explanation..
As you can see, I enjoy sharing what I know about melatonin.
It is a most fascinating and important molecule.
> Regards,
Best wishes to you!
Jo
+-----------------------------------+-----------------------------------------+
| Jo Robinson | jor at teleport.com |
| (503)284-4676 | 2826 NE 18th Portland, OR 97212 |
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