Tetrodotoxin (TTX) was intramuscularly administered to artificially hybridized specimens of the pufferfish Takifugu rubripes and T. niphobles to investigate toxin accumulation in hybrids, and TTX transfer/accumulation profiles in the pufferfish body. In the test fish administered 146 MU TTX in physiologic saline, TTX rapidly transferred from the muscle via the blood to other organs. Toxin transfer to the ovary rapidly increased to 53.5 MU/g tissue at the end of the 72-h test period. The TTX content in the liver and skin was, at most, around 4 to 6 MU/g tissue, and in the testis it was less than 0.01 MU/g tissue. On the other hand, based on the total amount of toxin per individual (% of the administered toxin), the skin and the liver contained higher amounts (20%-54% and 2%-24%, respectively), but the amount in the liver rapidly decreased after 8 to 12 h, and fell below the level in the ovary after 48 h. These findings suggest that part of the TTX is first taken up in the liver and then transferred/accumulated in the skin in male specimens and in the ovary in female specimens.

Tetrodotoxin (TTX) was administered to artificially hybridized specimens of the pufferfish Takifugu rubripes and Takifugu porphyreus to investigate toxin accumulation in hybrids and TTX transfer/accumulation profiles in the pufferfish body. In test fish administered TTX-containing feed homogenate at a dose of ~400 MU/fish by oral gavage using a syringe (OGA group), the toxin content (MU/g tissue) of the digestive tract rapidly decreased and that of the liver increased from 1 to 24 h after administration. From 24 to 120 h, the toxin content of the liver decreased gradually, and the toxin appeared in the skin. On the other hand, intramuscularly administered TTX (400 MU/ fish) was rapidly transferred to the liver and skin via the blood, and only a little toxin remained in the muscle even at 1 h (IMA group). The total amount of toxin remaining in the whole body (% of administered toxin) was 31-45% in the OGA group, and 42-74% in the IMA group; the scores in the OGA group were generally lower than those in the IMA group. In both OGA and IMA groups, the greatest amount of toxin accumulated in the liver (23-52%) after 8 h, followed by the skin (11-21%) after 72 h. The TTX administration experiment, especially using the oral gavage administration method, revealed that skins and livers of torama pufferfish hybrid are endowed with TTX-accumulating ability, but the muscles are not, and that TTX taken up from toxic feed to the pufferfish body is transferred first to the liver and then to the skin via the blood.