Toxic substances and health

Author: (Japanese) Yasushi Oki
Publisher:
Publish Date: 2006-11-01
Features: Pufferfish
Discovered by the Japanese as highly toxic
As the saying goes, "desire to eat pufferfish but fear of death," pufferfish are indeed a rare delicacy, but cases of poisoning from eating them are not uncommon.
Nowadays, people can confidently enjoy pufferfish prepared by chefs who have passed national exams, but even so, they can't help but feel uneasy while savoring its flavor.
The toxicity of pufferfish is not only found in the ovaries and liver but also in the testes and intestines. Some pufferfish skin is also toxic, but the meat itself is harmless and delicious. Because of this, pufferfish have become a subject that food enthusiasts are eager to taste yet remain wary of. The poison found in pufferfish is known as "tetrodotoxin," a highly toxic substance with a median lethal dose of just 0.01 milligrams. However, its toxicity can vary slightly depending on the individual pufferfish and the season.
Symptoms of pufferfish poisoning first manifest as restlessness, followed by vomiting, and then muscle paralysis around the lips, tongue, and fingertips, leading to difficulty swallowing. In severe cases, it can cause loss of consciousness, blood pressure drops, respiratory failure, and even death. Unfortunately, even in today's medically advanced world, no effective antidote for pufferfish poisoning has been found. Treatment for poisoned individuals can only involve symptomatic measures, such as inducing vomiting, gastric lavage, taking laxatives, and artificial respiration.
However, in most cases, even if someone is poisoned by pufferfish, they can survive if they endure for 9 to 10 hours. Japan, which has long regarded pufferfish as a delicacy, is a global leader in the study of pufferfish toxin. Research on pufferfish toxin began in the mid-Meiji era, with the formal naming of "tetrodotoxin" in 1908 (Meiji 42). In 1950, following World War II, researchers successfully achieved the crystallization and separation of pufferfish toxin.
Professor Kyoichi Tsuda of Tokyo University and Professor Yoshinori Hirata of Nagoya University independently conducted X-ray structural analyses of pufferfish toxin, clarifying its chemical structure and gaining worldwide attention. According to their research, pufferfish toxin is a low-molecular-weight poison highly similar to plant alkaloids, differing significantly from other animal toxins that belong to protein toxins.
It has long been known that pufferfish toxin is a unique poison that strongly paralyzes skeletal muscle. In 1964, Dr. Toshio Takahashi, who taught at Duke University in the U.S., confirmed this observation at the molecular level. He pointed out that pufferfish toxin enters the sodium ion channels that generate electrical currents in nerves, forcibly interrupting neural transmission, leading to paralysis of skeletal and cardiac muscles.
Interestingly, pufferfish toxin has no effect on smooth muscle, which is found in internal organs. This is because smooth muscle activity does not rely on sodium ion channels but on potassium ion channels.
According to a 1983 report by a research team from the Faculty of Agriculture at Tokyo University, pufferfish toxin is produced when pufferfish consume the prey flower Clione. If this report is accurate, then pufferfish toxin may originate from microorganisms (plankton), much like shellfish toxins.