Effect of maitotoxin on sea urchin egg fertilization and on Ca2+ permeabilities of eggs and intracellular stores.
Maitotoxin (MTX), a potent marine toxin involved in ciguatera poisoning, inhibited sea urchin egg fertilization in a dose-dependent manner with an IC50 of 7.5 x 10(-3) MU (mouse-unit)/ml. It did not affect male gametes fertilizing capabilities but provoked exocytosis in female gametes. It induced a K+ loss simultaneously with a Na+ entry into unfertilized eggs and increased the Ca2+ influx at higher concentrations. On isolated cortex preparations, high concentrations of MTX reduced the rate of ATP-dependent Ca2+ accumulation into reticulum compartments and caused a leakage of Ca2+ from a preparation pre-loaded with 45Ca2+. Verapamil (10(-4) M) similarly blocked the increase of egg permeability to Ca2+ and the effect on Ca2+ sequestering into intracellular compartment, induced by MTX. Ion transport perturbations which evolved relatively slowly are probably not the direct cause of fertilization inhibition which could be related to a modification of the plasma membrane of the female gametes by this hydrophilic toxin.
Pesando
D
D
Unité 303 INSERM, Villefranche-sur-Mer, France.
Girard
J P
JP
Durand-Clément
M
M
Payan
P
P
Puiseux-Dao
S
S
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D005306:Fertilization / Q000187:drug effects*; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008387:Marine Toxins / Q000302:isolation & purification / Q000494:pharmacology*; D010063:Ovum / Q000187:drug effects / Q000502:physiology*; D035964:Oxocins; D011188:Potassium / Q000378:metabolism; D012617:Sea Urchins; D012964:Sodium / Q000378:metabolism; D013094:Spermatozoa / Q000187:drug effects / Q000502:physiology*; D014700:Verapamil / Q000494:pharmacology; D000095702:Polyether Toxins
D002118:Calcium; D008387:Marine Toxins; D035964:Oxocins; D011188:Potassium; D012964:Sodium; D014700:Verapamil; C020394:maitotoxin; D000095702:Polyether Toxins