Lethal anatoxin

The developed biosensor was applied to the analysis of cyanobacterial bloom samples from freshwater lakes of Spain, Greece, France, Scotland and Denmark. Two samples from Scotland and one from Denmark irreversibly inhibit the acetylcholinesterase. The estimated concentrations were between 1.5 and 30nmol/g of dry weight, values extremely high when compared to the intraperitoneal 50% lethal dose of anatoxin-a(s) in mice (121 nmol/kg). 

A report suggests that the intravenous administration of a cell-free extract of Anabaena flos-aquae (containing anatoxin-a) produced a transient vasodepressor response followed by a sustained rise in blood pressure in rats. Prolonged apnoea with attendant bronchoconstriction was observed, which remained unaltered by atropine. However, the statement by these authors that AN should be considered as a weapon of mass destruction, mainly due to its lethal anticholinesterase activity (Dube et al. 1996), raises the possibility of confusion with anatoxin-a(s) since AN is a nicotinic agonist and not a cholinesterase inhibitor. 

Microcystis, Nostoc, and Oscillatoria (Planktothrix). Cyanobacteria toxins (cyanotoxins) include cytotoxins and biotoxins (neurotoxins anatoxin-a, anatoxin-a(s) and saxitoxins, and the hepatotoxins microcystins MCs, and nodularins), with biotoxins being responsible for acute lethal, acute chronic, and subchronic poisonings of wild/domestic animals and humans. In most of the reported cases, afflicted animals consumed water from water bodies where there was an obvious presence of cyano-bacterial scum on the water surface. More recent measurements of cyanobacterial toxins using sensitive modem analytical methods have often revealed high frequencies of toxic blooms even when animal poisonings have not been reported. 

Anatoxin-a(s) (Fig. 3.4) was discovered by Mahmood and Carmichael as a metabolite of Anabaena flos-aquae NRC 525-17 [4, 5]. This toxin was implicated in the death of wild animals (ducks, birds, swine) after ingestion of contaminated water. This cyanotoxin is a neurotoxin, but different from anatoxin-a, and this unique alkaloid is an irreversible inhibitor of acetylcholine esterase with a toxicology similar to that of known anticholinesterases such as paraoxon [116-119]. Anatoxin-a(s) provokes salivation (thus the suffix (s)), chromodacryorrhea, fascic-ulation, and urinary incontinence, and death within 7-20 min, on rats treated with 0.25-1.0 mg kg (i.p.) The lethal dose LD50 (mouse, i.p.) is 50 pg kg"" making... 

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