THe antioxidant properties of melatonin

[skim at ALLIANT.SNU.AC.KR]

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.

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?

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?

4. Is there any site other than pineal gland that can produce melatonin?

5. How about long-term toxicity of melatonin supplementation? or Is it possible
that withdrawal of supplement does harm to people?

I hope not bothering you much.
Thank you in advance for your explanation..
Regards,

Seong-Hun Kim