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Name:  Roxanna
Status: student
Grade: 9-12
Location:CA
Country: N/A
Date: 5/9/2005


Question:
I am a chemistry student and we are learning of all the different types of alcohols. I was wondering what is in methanol that makes people go blind?


Replies:
Roxanna,

A biochemist will probably do a better job at answering your question, but I'll give it a shot. When methanol (CH3OH) is ingested, it is acted upon by an enzyme called alcohol dehydrogenase and the result is the production of formaldehyde (CH2O). [You will note that the net effect is the removal of two hydrogens and the formation of a double-bond between the carbon and oxygen.] Formaldehyde can migrate to the brain where it can damage the optic nerves (I am not sure if it is clearly known how this happens).

Greg (Roberto Gregorious)


Hi Roxanna

If ingested, methanol undergoes dehydrogenation in the liver by the way of a local enzyme and formaldehyde is produced as a result. Formaldehyde and related compounds such as formic acid have a huge ocular toxicity, the vision becomes blurred, it happens a central scotoma (central vision is lost) and eventually blindness happens.

Methanol toxicity in humans (also in monkeys) is characterized by a latent period of many hours followed by a metabolic acidosis and ocular toxicity. The metabolic acidosis and blindness is apparently due to formic acid accumulation in humans and monkeys. The accumulation of formate is due to a deficiency in formate metabolism which is, in turn, related, in part, to low hepatic tetrahydrofolate (H4 folate).

Thanks for asking NEWTON!

Mabel
(Dr. Mabel M. Rodrigues)


Roxanna,

Methyl alcohol possesses distinct narcotic properties. Its main toxic effect is exerted upon the nervous system, particularly the optic nerves and possibly the retinae. The effect upon the eyes has been attributed to optic neuritis, which subsides but is followed by atrophy of the optic nerve. Once absorbed into the body, methanol is only very slowly eliminated. Coma resulting from massive exposures may last up to 2-4 days. In the body, the products formed by methanol oxidation are formaldehyde and formic acid, both of which are toxic. I trust that this helps.

Sincerely,
Bob Trach



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