Purification and characterisation of large and small maitotoxins from cultured Gambierdiscus toxicus.
Three strains of cultured Gambierdiscus toxicus yielded distinct maitotoxins (maitotoxin-1, -2, and -3) which were purified to homogeneity by high pressure liquid chromatography. Maitotoxins-1 and -2 are large toxins (molecular weights for the sodium salts = 3,422 and 3,298, respectively), whereas maitotoxin-3 is relatively small (molecular weight = 1,060 for the sodium salt). The contractile actions on isolated guinea-pig left atria, vas deferens and ilea of maitotoxins-1 and -2 were compared with those of the small maitotoxin, maitotoxin-3. Maitotoxin-1, -2 and -3 each produced quantitatively similar, concentration-dependent patterns of positive and negative inotropy in atria when compared on a mouse unit/ml basis (one mouse unit is the intraperitoneal LD50 dose for a 20 g mouse; the LD50 for maitotoxin-2 = 0.08 microgram/kg). Concentrations of maitotoxin-2 greater than 5 x 10(-13) M caused positive inotropy. The three maitotoxins produced patterns of contractions in vas deferens and ilea that were qualitatively similar, including a period of prominent spike activity in vas deferens. On a mouse unit/ml basis, the order of potency on smooth muscle was maitotoxin-1 > maitotoxin-3 > maitotoxin-2. The contractile responses of smooth muscle to the maitotoxins were followed by an inhibitory phase where control agonist responses could not be elicited. The maitotoxin-induced contractile responses of vas deferens were inhibited by nicardipine but not phentolamine, indicating that in this tissue, each maitotoxin has mainly a direct contractile effect that requires calcium influx through voltage-sensitive calcium channels.(ABSTRACT TRUNCATED AT 250 WORDS)
Holmes
M J
MJ
Southern Fisheries Centre, Queensland Department of Primary Industries, Australia.
Lewis
R J
RJ
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004141:Dinoflagellida; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D008297:Male; D008387:Marine Toxins / Q000302:isolation & purification* / Q000494:pharmacology / Q000633:toxicity; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009200:Myocardial Contraction / Q000187:drug effects; D035964:Oxocins; D013045:Species Specificity; D014649:Vas Deferens / Q000187:drug effects; D000095702:Polyether Toxins
D008387:Marine Toxins; D035964:Oxocins; C020394:maitotoxin; D000095702:Polyether Toxins