Apparent Lack of tetrodotoxin Biosynthesis in Captured Taricha torosa and Taricha granulosa

Abstract

In order to explore the origin of the potent neurotoxin tetrodotoxin, feeding experiments were carried out using [2-14C]-acetate, [guanido-14C]-arginine, [ureido-14C]-citrulline and [14C(U)]-glucose on the newts Taricha torosa and Taricha granulosa. The precursors were administered by injection, by oral feeding, or by soaking the newts in a bath of water containing the radioactive precursors. None of these feeding experiments resulted in the incorporation of radioactivity into tetrodotoxin, though common metabolites such as cholesterol, amines, amino acids, and macromolecular compounds were significantly labeled. The toxicities of T. granulosa and T. torosa used for the experiment were found to be higher than those previously reported. They retained a high level of toxicity during their captivity, yet they were found to continuously release small amounts of toxins (2.5% of the total toxins in one year). When subjected to an electric shock, the newts released significant amounts of toxin. © 1983, The Pharmaceutical Society of Japan. All rights reserved.