Tetrodotoxin/Saxitoxins Selectivity of the Euryhaline Freshwater Pufferfish Dichotomyctere fluviatilis

Abstract

The present study evaluated differences in the tetrodotoxin (TTX)/saxitoxins (STXs) selectivity between marine and freshwater pufferfish by performing in vivo and in vitro experiments. In the in vivo experiment, artificially reared nontoxic euryhaline freshwater pufferfish Dichotomyctere fluviatilis were intrarectally administered a mixture of TTX (24 nmol/fish) and STX (20 nmol/fish). The amount of toxin in the intestine, liver, muscle, gonads, and skin was quantified at 24, 48, and 72 h. STX was detected in the intestine over a long period of time, with some (2.7–6.1% of the given dose) being absorbed into the body and temporarily located in the liver. Very little TTX was retained in the body. In the in vitro experiments, slices of the intestine, liver, and skin tissue prepared from artificially reared nontoxic D. fluviatilis and the marine pufferfish Takifugu rubripes were incubated in buffer containing TTX and STXs (20 nmol/mL each) for up to 24 or 72 h, and the amount of toxin taken up in the tissue was quantified over time. In contrast to T. rubripes, the intestine, liver, and skin tissues of D. fluviatilis selectively took up only STXs. These findings indicate that the TTX/STXs selectivity differs between freshwater and marine pufferfish.

Tetrodotoxin/Saxitoxin Accumulation Profile in the Euryhaline Marine Pufferfish Chelonodontops patoca

“…From the ovaries of T. rubripes , TTX with a purity greater than 60% was prepared, and from the xanthid crab Zosimus aeneus , STX with a purity greater than 80% was prepared by solvent partitioning, activated charcoal treatment, and Bio-Gel P-2 (Bio-Rad Laboratories, Inc., Hercules, CA, USA) and Bio-Rex 70 (Bio-Rad) column chromatography according to the previously reported method [ 37 ], and used for the intrarectal TTX/STX administration experiment. Crystalline TTX (Wako Pure Chemical Industries Ltd., Tokyo, Japan) and an aqueous solution of STX purified from the xanthid crab Z. aeneus were used as external standards for the toxin quantification analyses described below.…”

“…In our previous TTX/STXs administration experiments using marine/freshwater pufferfish [ 13 , 14 , 33 , 37 ], good results were obtained at doses of ~1–2.6 nmol/g body weight. Since the test fish used in this study, however, were very small (body weight, 1.51 ± 0.27 g), we set the dose of both TTX and STX to ~5 nmol/g body weight (7.5 nmol/fish) to ensure the necessary toxin amount for analysis.…”

“…TTX and STX were quantified by liquid chromatography-tandem mass spectrometry and high-performance liquid chromatography with post-column fluorescence derivatization, respectively, according to previously reported methods [ 37 ].…”

“…Our findings revealed that T. pardalis and P. suvattii selectively take up and accumulate TTX and STXs, respectively [ 33 ]. In addition, tissue slice incubation experiments using the liver and other tissues showed that when TTX/STXs are present, the tissues of Takifugu rubripes selectively take up TTX [ 34 , 35 , 36 ] and tissues of the Dichotomyctere fluviatilis (a euryhaline freshwater pufferfish) selectively take up STXs [ 37 ]. Thus, the ratio of TTXs/STXs in a pufferfish is dependent not only on the abundance of TTXs/STXs in its habitat (external factor), but also on its inherent TTXs/STXs selectivity (internal factor).…”

Cytotoxic Activities, Determining Toxin, and Molecular Docking of Ovary Pufferfish (Tetraodon leiurus) in Singkarak Lake as Cancer Chemoprevention Candidate

“…Neurotoxins that are present in pufferfish include TTX and STX 12 . STX can affect muscle and nerve conduction and selectively block voltage-gated sodium (NaV) channels, it may cause death and respiratory paralysis.…”