title: Contraction and increase in tissue calcium content induced by maitotoxin, the most potent known marine toxin, in intestinal smooth muscle.
abstract: Maitotoxin (MTX), the most potent known marine toxin, isolated from toxic dinoflagellates and poisonous fish, caused a dose-dependent contraction of the guinea-pig isolated ileum and taenia caeci at concentrations of 100 pg to 30 ng/ml. These contractile responses to MTX (3 ng/ml) in both tissues were abolished by incubation in Ca2+-free solution and were markedly inhibited by treatment with methoxyverapamil (D600), but were not affected by tetrodotoxin and atropine. Furthermore, MTX markedly elevated tissue Ca2+ content of the taenia caeci. These results suggest that MTX activates Ca2+ channels in the smooth muscle membrane of both tissues to increase Ca2+ influx and thus induces contractions.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002432:Cecum / Q000187:drug effects / Q000378:metabolism; D005711:Gallopamil / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D008387:Marine Toxins / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D035964:Oxocins; D000095702:Polyether Toxins
chemical_list: D002118:Calcium; D005711:Gallopamil; D008387:Marine Toxins; D035964:Oxocins; C020394:maitotoxin; D000095702:Polyether Toxins