The metabolic source of tetrodotoxin is uncertain. No algal source has been identified, and until recently tetrodotoxin was assumed to be a metabolic product of the host. However, recent reports of the production of tetrodotoxin/anhydrotetrodotoxin by several bacterial species, including strains of the family Vibrionaceae, Pseudomonas sp., and Photobacterium phosphoreum, point toward a bacterial origin of this family of toxins.
To investigate the genes related to the biosynthesis or accumulation of tetrodotoxin (TTX) in pufferfish, mRNA expression patterns in the liver from pufferfish, akamefugu Takifugu chrysops and kusafugu Takifugu niphobles, were compared by mRNA arbitrarily primed reverse transcription-polymerase chain reaction (RAP RT-PCR) with fish bearing different concentrations of TTX and its derivatives. RAP RT-PCR provided a 383 bp cDNA fragment and its transcripts were higher in toxic than non-toxic pufferfish liver. Its deduced amino acid sequence was similar to those of fibrinogen-like proteins reported for other vertebrates. Northern blot analysis and rapid amplification of cDNA ends (RACE) revealed that the cDNA fragment of 383 bp was composed of at least three fibrinogen-like protein (flp) genes, flp-1, flp-2 and flp-3. Relative mRNA levels of flp-1, flp-2 and flp-3 showed a linear correlation with toxicity of the liver for two pufferfish species.
IDENTIFICATION AND USE: Tetrodotoxin (TTX) is a solid. TTX contained in puffer, has become an extremely popular chemical tool in the physiological and pharmacological laboratories since discovery of its channel blocking action in the early 1960s. More recently, the TTX-resistant sodium channels have been discovered in the nervous system and received much attention because of their role in pain sensation. TTX is now known to be produced not by puffer but by bacteria, and reaches various species of animals via food chain. HUMAN STUDIES: TTX is a deadly neurotoxin which selectively inhibits Na(+) activation mechanism of nerve impulse, without affecting the permeability of K(+) ions. TTX interferes with the transmission of signals from nerves to muscles by blocking sodium channels. This results in rapid weakening and paralysis of muscles, including those of the respiratory tract, which can lead to respiratory arrest and death. TTX poisoning may either have rapid onset (10 to 45 minutes) or delayed onset (generally within 3 to 6 hours but rarely longer). Death may occur as early as 20 minutes, or as late as 24 hours, after exposure; but it usually occurs within the first 4 to 8 hours. Patient/victims who live through the acute intoxication in the first 24 hours usually recover without residual deficits. Symptoms may last for several days and recovery takes days to occur. Upon ingestion, at first stage TTX producing numbness and sensation of prickling and tingling (paresthesia) of the lips and tongue, followed by facial and extremity paresthesias and numbness, headache, sensations of lightness or floating, profuse sweating (diaphoresis), dizziness, salivation (ptyalism), nausea, vomiting (emesis), diarrhea, abdominal (epigastric) pain, difficulty moving (motor dysfunction), weakness (malaise), and speech difficulties. At the second stage there is increasing paralysis, first in the extremities, then in the rest of the body, and finally in the respiratory muscles; difficulty breathing or shortness of breath (dyspnea); abnormal heart rhythms (cardiac dysrhythmias or arrhythmia); abnormally low blood pressure (hypotension); fixed and dilated pupils (mydriasis); coma; seizures; respiratory arrest; and death. A number of case reports describe food poisoning with TTX. Most of these poisoning episodes occur from home preparation and consumption and not from commercial sources of the pufferfish. TTX was shown to lack genotoxic activity in vitro in human lymphocytes with or without metabolic activation. ANIMAL STUDIES: The clinical symptoms and signs of TTX poisoning in dogs treated with TTX by iv infusion were similar to those of anticholinesterase poisoning. TTX was found to be about fifty times less toxic and to have more delayed death occurrence to mice via oral route than that via i.p. injection. In rats brain serotonin level was significantly increased and reached its peak level after 4 hours of TTX administration. Brain acetylcholine, histamine, and norepinephrine levels were also significantly increased but reached peak level after 6 hours. The effect of the gonad extract from pufferfish was more significantly profound and of longer duration than the skin extract. On the other hand, brain epinephrine did not show any significant change during the experimental period. TTX administered iv in male rabbits at sublethal levels produced shock due to perfusion failure with lactacidemia, hypoproteinemia, increased bleeding time, decreased red cell mass, and decreased platelet count. The severity of poisoning was proportional to the magnitude of tetrodotoxin given. Hemorrhages in brain, liver, lung, and diaphragm were observed in necropsy study. Significant differences in susceptibility to TTX were found among five mouse strains tested. TTX was clearly shown to lack in vitro or in vivo genotoxic activity. ECOTOXICITY STUDIES: TTX and its analogs (TTXs), widely distributed among marine as well as terrestrial animals, induce dangerous intoxications. Besides helping to deter predators, TTX resistance enables pufferfishes to selectively feed on TTX-bearing organisms. However TTXs do not protect flatworms from Guam from their predators but instead are used to capture mobile prey.
来源:Hazardous Substances Data Bank (HSDB)
毒理性
副作用
神经毒素 - 其他中枢神经系统神经毒素
Neurotoxin - Other CNS neurotoxin
来源:Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
The ability of a tetrodotoxin (TTX)-specific monoclonal antibody to confer passive protection against lethal TTX challenge was investigated. The monoclonal antibody, T20G10, has an estimated affinity for TTX of approximately 10-9 M and is about 50-fold less reactive with anhydrotetrodotoxin and unreactive with tetrodonic acid by competitive immunoassay. T20G10 specifically inhibited TTX binding in an in vitro radioligand receptor binding assay, but had no effect on the binding of saxitoxin to the sodium channel on rat brain membranes. In prophylaxis studies, mice were administered T20G10 via the tail vein 30 min prior to i.p. TTX challenge (10 ug/kg). Under these conditions, 100 micrograms T20G10 protected 6/6 mice, whereas 3/6 mice were protected with 50 micrograms T20G10. Non-specific control monoclonal antibody did not protect against lethality. Therapy studies simulating oral intoxication were performed with mice given a lethal dose of TTX by gavage in a suspension of non-fat dry milk in phosphate-buffered saline. Death occurred within 25-35 min in 6/6 mice not treated with T20G10. However, 500 ug T20G10 administered via the tail vein 10-15 min after oral TTX exposure prevented death in 6/6 mice. Lower doses of mAb conferred less protection.
At 24 hours after coronary artery occlusion in dogs, lidocaine (4 mg/kg, iv) and tetrodotoxin (2 ug/kg, iv) showed marked antiarrhythmic activity. At 2-fold lower doses, neither substance alone had an effect on arrhythmias, but when administered together, they induced almost complete restoration of cardiac rhythm.
来源:Hazardous Substances Data Bank (HSDB)
毒理性
相互作用
蟾毒素增加了突触体对钠的摄取。藜芦碱也增加了钠的摄取。河豚毒素阻断了上述毒素的效果。
Batrachotoxin increased sodium uptake by synaptosomes. Veratridine also increased the sodium uptake. Tetrodotoxin blocked the effects of the above toxins.
Twenty-three specimens of a tree-frog Polypedates sp. were collected from two locations (Mymensingh and Barisal) of Bangladesh in 1999, and assayed for their toxicity scores and toxin principle. Among the tissues, only the skin of the Mymensingh specimens was found to be toxic in mouse test, with the toxicity scores of 31-923 ug/g. The toxin isolated from the skin was analyzed by high-performance liquid chromatography, electrospray ionization-time of flight mass spectrometry and proton nuclear magnetic resonance, and characterized as tetrodotoxin, a toxin principle.
Tetrodotoxin (TTX) and its analogs (TTXs), widely distributed among marine as well as terrestrial animals, induce dangerous intoxications. These highly potential toxins are also known as the causative agent of puffer fish poisoning. ... TTX, anhydrotetrodotoxin, 11-deoxytetrodotoxin and trideoxytetrodotoxin were determined in separated tissues of Bangladeshi marine puffers, Takifugu oblongus. TTX was predominant in skin, muscle and liver, whereas trideoxytetrodotoxin preponderated in the ovary. The toxicity of the various tissues was determined by a mouse bioassay.
To investigate the relationship between the toxicity of puffer fish and the distribution of tetrodotoxin-producing bacteria in puffer fish Fugu rubripes collected from the Bohai Sea of China, bacteria were isolated from each organ (ovaries, livers, intestines and gallbladders) and screened for tetrodotoxin (TTX) production. 20 out of 36 isolated strains were found to produce TTX in vitro. In the organs of ovaries and livers whose toxicity is more potent than other organs, the number and toxicity of TTX-producing strains was greater than that of others. Most TTX-producing bacterial strains were identified as Bacillus spp. (19 strains) and Actinomycete spp. (1 strain) based on the morphological observation, physiological and biochemical characteristics and G+C content of DNA. The purified toxin was identified to be TTX by high performance liquid chromatography assay, thin-layer chromatography assay and electrospray ionization mass spectrometry analysis. Our results suggested that TTX-producing bacteria are closely related to the toxification of the puffer fish. More research is needed to elucidate the mechanism of TTX synthesis and the role of TTX in bacteria.
The liver homogenate of puffer fish was fractionated into blood cell, nuclear, mitochondrial, microsomal and cytosol fractions by the differential centrifugation method. ... Analyses by HPLC and LC-FABMS demonstrated that tetrodotoxin is the major toxic principle in each fraction. These results reveal that tetrodotoxin is widely distributed in organelles in liver cells, though predominantly in the cytosol fraction.
