Tetrodotoxin Poisoning Due to Smooth-backed Blowfish Lagocephalus inermis and Toxicity of L. inermis Caught off the Kyushu Coast, Japan

摘要

2008年10月に長崎県でフグ中毒が発生した.中毒残品の筋肉からDNAを抽出精製し，PCR増幅したミトコンドリアDNA 16S rRNAおよびシトクロムb部分領域の塩基配列はカナフグのそれと一敦した.中毒残品の肝臓試料から1，230MU/gの毒性とテトロドトキシン（TTX）が検出されたことから，本中毒はカナフグによるTTX中毒と判断した.中毒原因個体の肝臓試料からこれまでの報告を上回る猛毒レベル（≧1，000MU/g）の毒性が検出されたため，九州沿岸で漁獲されたカナフグ13検体の毒性を調べた.12検体が有毒で，これまで無毒とされていた腸や卵巣も毒性を示し，毒性が不明だった腎臓，胆のう，牌膿からは弱毒レベルの毒性が高頻度で検出され，日本産カナフグの毒性の見直しが必要と考えられた.%Food poisoning due to ingestion of a puffer fish occurred in Nagasaki Prefecture, Japan, in Oc­tober 2008, causing neurotoxic symptoms similar to those of tetrodotoxin (TTX) poisoning. In the present study, we identified the species, toxicity, and toxins using the remaining samples of the causative puffer fish. The puffer fish was identified as smooth-backed blowfish Lagocephalus iner­mis by nucleotide sequence analysis of the 16S rRNA and cytochrome b gene fragments of muscle mitochondrial DNA. The residual liver sample showed toxicity as high as 1,230 mouse unit (MU)/g by bioassay and TTX was detected by liquid chromatography/mass spectrometry analysis. We therefore concluded that the food poisoning was due to TTX caused by consumption of the toxic liver of L. inermis. This is the first report that the liver of L. inermis caught in Japanese waters is strongly toxic, with levels exceeding 1,000 MU/g. In this context, we re-examined the toxicity of L. inermis collected off the coast of Japan. Of 13 specimens assayed, 12 were toxic, although the toxici­ty varied markedly among individuals and tissues. Because the intestine and ovary of L. inermis have been considered non-toxic, it is particularly noteworthy that these organs were determined to be toxic, with a maximum toxicity of 43.6 MU/g and 10.0 MU/g, respectively. Furthermore, kidney, gallbladder, and spleen, whose toxicity has been unknown, were frequently found to be weakly toxic with levels ranging from 10 to 99 MU/g. Therefore, further study is needed to re-examine the toxici­ty of smooth-backed blowfish L. inermis in the coastal waters of Japan.