Chronic In Vivo Effects of Repeated Exposure to Low Oral Doses of Tetrodotoxin: Preliminary Evidence of Nephrotoxicity and Cardiotoxicity

Tetrodotoxin (TTX) is one of the most potent naturally occurring neurotoxins. Initially TTX was associated with human food intoxications in Japan, but nowadays, concerns about the human health risks posed by TTX have increased in Europe after the identification of the toxin in fish, marine gastropods, and bivalves captured in European waters. Even when TTX monitoring is not currently performed in Europe, an acute oral no observable effect level (NOAEL) of 75 g/kg has been recently established but, to date, no studies evaluating the chronic oral toxicity of TTX have been released, even when EFSA has highlighted the need for them. Thus, in this work, the chronic effects of low oral TTX doses (below the acute lethal dose 50) were evaluated following internationally adopted guidelines. The results presented here demonstrate that low oral doses of TTX have deleterious effects on renal and cardiac tissues. Moreover, alterations in blood biochemistry parameters, urine production, and urinalysis data were already detected at the oral dose of 75 mu g/kg after the 28 days exposure. Thus, the data presented here constitute an initial approach for the chronic evaluation of the in vivo toxicity of tetrodotoxin after its ingestion through contaminated fishery products.