Quantitative analysis of toxin extracts from various tissues of wild and cultured puffer fish by an electrophysiological method.

We observed the effects of the toxin extracted from various tissues of wild and cultured puffer fish on voltage-dependent sodium current (I(Na)) using single rat CA1 neurons, and compared the results with that of tetrodotoxin (TTX). Toxin extracts from wild puffer fish inhibited I(Na) in a dilution-dependent manner, and toxin extracts from liver or ovary produced 300 times greater inhibition than that from muscle, and corresponded to about 65 microg TTX/g tissue. We also used puffer fish cultured in net cages or in tanks set up on land, in an attempt to isolate them from the food chain. The toxin extracts from cultured puffer fish also suppressed I(Na), but the inhibition was much weaker, and the effects of toxin extracts were almost the same in all tissues examined including liver, ovary, muscle, etc. We calculated the maximum edible amount for each tissue, assuming that the lethal dose of TTX is 1-10 microg/kg, and we found that the liver or ovary was edible in the case of cultured puffer fish.

Inhibition of Na currents by the toxin extracts from puffer fishes captured in the sea coast of Japan.

The inhibitory effects of toxin extracted from muscle or liver of five different puffer fishes (hereafter referred as puffer(s)) captured on the Japanese sea coast were examined on voltage-dependent sodium current (I(Na)) recorded from dissociated single rat hippocampal CA1 neurons. The inhibitory effects estimated from IC(50) values of toxin extracts on I(Na) were in the order of Takifugu vermicularis > Lagocephalus wheeleri > Canthigaster rivulata > Takifugu rubripes > Arothron reticularis from muscle and T. vermicularis > T. rubripes > L. wheeleri > A. reticularis > C. rivulata from liver, thereby indicating that the amount of toxin in the liver or muscle differs between puffers. In addition, the present results indicate that the muscle of T. vermicularis, which is eaten in Japan, contains relatively higher amounts of toxin compared to those of T. rubripes, also eaten. This observation suggests that caution should be taken concerning the maximal edible amount of muscle prepared from T. rubripes.