maitotoxin and fura-2-am

Maitotoxin, a potent marine toxin isolated from toxic tropical dinoflagellates and poisonous fishes induces contraction of different smooth muscle preparations. Actions of maitotoxin on phosphoinositides and calcium metabolism were studied using a primary culture of aortic smooth muscle cells. Maitotoxin induced a very large increase of cytosolic calcium concentration as evaluated by fura-2 acetoxymethyl ester fluorescence. This increase was concomitant with stimulation of inositol-phosphate accumulation and loss of viability of aortic smooth muscle cells. These responses to maitotoxin were abolished in Ca2+-free medium, and were mimicked by saponin. Calcium ionophores or K+ depolarisation did not induce inositol-phosphate formation. These results suggest that maitotoxin acts by altering smooth muscle cells permeability allowing a sustained calcium influx which is able to activate inositol-phosphate formation and which is lethal for the cells.

Topics: Angiotensin II; Animals; Aorta, Thoracic; Benzofurans; Calcium; Cell Survival; Cells, Cultured; Fluorescent Dyes; Fura-2; Male; Marine Toxins; Muscle, Smooth, Vascular; Oxocins; Phosphatidylinositols; Potassium; Rats; Rats, Inbred Strains; Saponins; Spectrometry, Fluorescence