Toxins of Pufferfish—Distribution, Accumulation Mechanism, and Physiologic Functions

摘要

Our many years of studies have provided a lot of information regarding distribution,accumulation mechanism, and physiologic functions of the natural toxins harbored bypufferfish. We detected tetrodotoxin (TTX) and/or its derivatives in several species ofaquatic organisms including marine bacteria. This, along with the fact that pufferfishbecame non-toxic when they were reared with non-toxic feed, indicated that the toxificationof pufferfish is of exogenous origin. Subsequently, we revealed by various TTX administrationexperiments using non-toxic cultured pufferfish that the TTX administered intothe muscle or digestive tract rapidly transferred to the liver and skin, and that the toxintransfer to the gonads was largely different between male and female, suggesting theinvolvement of maturation in the internal kinetics of TTX. On the other hand, we visualizedmicro-distribution of TTX in the tissues of various TTX-bearing organisms using animmunohistochemical technique, giving a crucial insight to elucidate physiologic functionsof TTX including the function as a defensive or offensive agent. Furthermore, wefound that Southeast Asian freshwater pufferfish possess paralytic shellfish poison (PSP)as a main toxin, and that boxfish and Bangladeshi freshwater pufferfish bear a palytoxin(PLTX)-like toxin, and cause a rhabdomyolysis, which overturned the common sensethat pufferfish toxin equals TTX.