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Guanitoxin (GNT), formerly known as anatoxin-a(S) "Salivary", is a naturally occurring
cyanotoxin
Cyanotoxins are toxins produced by cyanobacteria (also known as blue-green algae). Cyanobacteria are found almost everywhere, but particularly in lakes and in the ocean where, under high concentration of phosphorus conditions, they reproduce exp ...
commonly isolated from cyanobacteria (specifically of the genus ''Anabaena'') and causes excess salivation in mammals via inhibition of acetylcholinesterase. Guanitoxin was first structurally characterized in 1989, and consists of a cyclic ''N''-hydroxyguanine organophosphate with a phosphate ester moiety.
Toxicity and treatment
The main mechanism of action for guanitoxin is by irreversibly inhibiting the active site of acetylcholinesterase leading to excess acetylcholine in the parasympathetic and peripheral nervous systems; inducing poisoning via nicotinic and muscarinic cholinergic receptor stimulation. The clinical signs of high level guanitoxin exposure consists mainly of excessive salivation,lacrimation
Tears are a clear liquid secreted by the lacrimal glands (tear gland) found in the eyes of all land mammals. Tears are made up of water, electrolytes, proteins, lipids, and mucins that form layers on the surface of eyes. The different types of ...
, chromodacryorrhea (in rats), urinary incontinence, muscular weakness, muscle twitching
A fasciculation, or muscle twitch, is a spontaneous, involuntary muscle contraction and relaxation, involving fine muscle fibers. They are common, with as many as 70% of people experiencing them. They can be benign, or associated with more serio ...
, convulsion, including opisthotonus
Opisthotonus or opisthotonos (from grc, ὄπισθεν, translit=opisthen, lit=behind and grc, τόνος, translit=tonos, lit=tension, label=none) is a state of severe hyperextension and spasticity in which an individual's head, neck and spinal ...
, and respiratory distress and/or failure.
Treatment of afflicted case by atropine has attested to suppress the muscarinic mediated toxicity; which prevents the namesake salivation that similarly reacts to prevent the toxin's other poisoning symptoms which include lacrimation, urinary incontinence and defecation. Atropine will not, however, counter another mechanism of the compounds toxicity as it also mediates a nicotinic adverse toxicity affecting muscle tremors, fasciculation, convulsions and respiratory failure.
Stability and degradation
Guanitoxin is generally labile. It decomposes rapidly in basic solutions, but is relatively stable in neutral or acidic solutions (pH 3-5). When stored at -20˚C, it slowly undergoes hydrolysis giving (5S)-5- dimethylamino)methyl2-imino-1-imidazolidinol and monomethyl-phosphate, and more slowly, formation of (S)-1-(2-iminoimidazolidin-4-yl)-N,N-dimethylmethanamine. Furthemore, air evaporation of guanitoxin resulted in significant hydrolysis to (5S)-5- dimethylamino)methyl2-imino-1-imidazolidinol.
See also
*Anatoxin-a
Anatoxin-a, also known as Very Fast Death Factor (VFDF), is a secondary, bicyclic amine alkaloid and cyanotoxin with acute neurotoxicity. It was first discovered in the early 1960s in Canada, and was isolated in 1972. The toxin is produced by mu ...
– a cyanotoxin that shares some clinical exposure signs, and also relates to the same cyanobacteria genera, but with a different chemical structure and toxic mechanism of action
*Paraoxon
Paraoxon is a parasympathomimetic which acts as an cholinesterase inhibitor. It is an organophosphate oxon, and the active metabolite of the insecticide parathion. It is also used as an ophthalmological drug against glaucoma. Paraoxon is on ...
– A synthetic pesticide with an analogous mechanism of action
References
{{Acetylcholine metabolism and transport modulators Acetylcholinesterase inhibitors Neurotoxins Guanidine alkaloids Organophosphates Methyl esters Cyanotoxins Nitrogen heterocycles Dimethylamino compounds Bacterial alkaloids