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Tetrodotoxin: Fugu Fish Toxin

Dateline: 04/24/00

By Alan Bruzel

Tetrodotoxin takes its name from the Tetraodontiformes, an order of fish possessing four prominent teeth (from tetras, four and odontos, tooth). It is a nerve-specific toxin present in a few species of this order; it is also found in some amphibians, crustaceans, mollusks, worms and algae. The toxin may originate from bacteria inhabiting the tissues of these marine creatures. Pseudoalteromonas haloplanktis tetraodonis, for example, is the source of tetrodotoxin in pufferfish.

Because of their delicious flavor, Japanese gourmets esteem meals prepared from pufferfish or blowfish (order Tetraodontiformes, genus Fugu). Those choosing to enjoy a fugu meal depend upon the skill of the licensed chef who must carefully remove the viscera of the fish, especially the liver and gonads where tetrodotoxin concentrations are the highest. A partiality to fugu is thus an expensive predilection, and, when prepared by the wrong hands, a dangerous one.

Toxic effects begin with a tingling and numbness of the lips and tongue. Depending upon the amount of toxin ingested (one milligram is believed to constitute a fatal dose), a progressive paralysis affects all muscular movement including that of the diaphragm. Most victims expire within six to twenty four hours. There is no known antidote; about fifty percent of poisoning victims die. Each year, about one hundred Japanese succumb to residual tetrodotoxin in fugu.

Tetrodotoxin inhibits nerve function by blocking the passage of sodium ions through the sodium ion channels of nerves. This prevents propagation of nerve impulses, which require unimpaired sodium ion movement. Tetrodotoxin gains entry to the sodium ion channel by using its positively charged guanidinium group to mimic the positively charged sodium cation. The remainder of the molecule confers stability to the tetrodotoxin-sodium ion channel complex. Studies on the Japanese tiger pufferfish, Fugu rubripes, show a single amino acid change in its sodium ion channel protein protects the fish from its own poison.

Tetrodotoxin

What the Web Has to Say about:
Tetrodotoxin: Fugu Fish Toxin

Blowfish and Trade
The danger and fascination with fugu – and its business aspect. From the Trade and the Environment Database.

Eye of Newt, Skin of Toad, Bile of Pufferfish
Startling accounts of tetrodotoxin toxicity and its links to zombification. From William Haugan Light in California Wild magazine.

HGMP-RC FUGU Project
F. rubripes is believed to have the same number of genes as humans, but has eight times less DNA. Data from the Human Genome Mapping Project Resource Center.

Ion Channels, Transmitters, Receptors and Disease
A look at ion channels responsible for nerve impulses. From the Neuromuscular Disease Center, Washington University School of Medicine.

Nobel Prize in Chemistry 1965
Awarded to organic chemist Robert Burns Woodward, who, among other accomplishments, determined the structure of tetrodotoxin.

Tetrodotoxin
Pufferfish and other organisms harboring this poison. From the Bad Bug Book, U.S. Food and Drug Administration.

Tetrodotoxin
Article by Jim Johnson reviewing the chemistry and pharmacology of this toxin. From the Molecule of the Month page, University of Bristol.

Toxicity: Tetrodotoxin
Treatment of patients with suspected tetrodotoxin poisoning. From Theodore Benzer, eMedicine.com.

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