Résumé
Maitotoxin is the most potent of the known marine toxins. The effect of maitotoxin on muscle contraction or hormone release was consistent with its action on the voltage-sensitive channel. Indeed, calcium antagonists such as nifedipine or diltiazem were able to reverse the maitotoxin effects. Using smooth muscle cells, we have analysed the effects of maitotoxin on the inositol phosphate metabolism. Maitotoxin stimulates the inositol phosphate formation (5 ± 1.8-fold in the presence of 10 mM LiCI). Moreover, this effect is not reversed, even partially by calcium antagonists, by α
1 antagonists and is not mimicked by Ca
2+ ionophores such as A23187 or calcium agonists such as Bay-K 8644. The action of maitotoxin is further discussed in this paper.