Involvement of carrier-mediated transport system in uptake of tetrodotoxin into liver tissue slices of puffer fish Takifugu rubripes.
Although puffer fish contain tetrodotoxin (TTX) at a high concentration mainly in liver, the underlying mechanism remains to be elucidated. In the present study, uptake of TTX into the liver tissue slices of puffer fish Takifugu rubripes was investigated by in vitro incubation experiment. When T. rubripes liver slices were incubated with 0-2000microM TTX at 20 degrees C for 60min, the uptake rates exhibited non-linearity, suggesting that the TTX uptake into T. rubripes liver is carrier-mediated. The TTX uptake was composed of a saturable component (V(max) 47.7+/-5.9pmol/min/mg protein and K(m) 249+/-47microM) and a non-saturable component (P(dif) 0.0335+/-0.0041microL/min/mg protein). The uptake of TTX was significantly decreased to 0.4 and 0.6 fold by the incubation at 5 degrees C and the replacement of sodium-ion by choline in the buffer, respectively, while it was not affected by the presence of 1mM l-carnitine, p-aminohippurate, taurocholate or tetraethylammonium. The TTX uptake by black scraper Thamnaconus modestus liver slices was much lower than that of T. rubripes and independent of the incubation temperature, unlike T. rubripes. These results reveal the involvement of carrier-mediated transport system in the TTX uptake by puffer fish T. rubripes liver slices.
Matsumoto
Takuya
T
Department of Food Science and Technology, Tokyo University of Marine Science and Technology, Konan 4-5-7, Minato, Tokyo 108-8477, Japan.
Nagashima
Yuji
Y
Kusuhara
Hiroyuki
H
Sugiyama
Yuichi
Y
Ishizaki
Shoichiro
S
Shimakura
Kuniyoshi
K
Shiomi
Kazuo
K
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects / Q000502:physiology; D002331:Carnitine / Q000494:pharmacology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D008051:Lipid Bilayers; D008099:Liver / Q000378:metabolism*; D023741:Takifugu / Q000502:physiology*; D013656:Taurocholic Acid / Q000494:pharmacology; D013696:Temperature; D019789:Tetraethylammonium / Q000494:pharmacology; D013779:Tetrodotoxin / Q000378:metabolism* / Q000493:pharmacokinetics; D010130:p-Aminohippuric Acid / Q000494:pharmacology
D002352:Carrier Proteins; D008051:Lipid Bilayers; D013779:Tetrodotoxin; D013656:Taurocholic Acid; D019789:Tetraethylammonium; D002331:Carnitine; D010130:p-Aminohippuric Acid