The effects of maitotoxin on phosphoinositides and calcium metabolism in a primary culture of aortic smooth muscle cells.
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.
Berta
P
P
Centre de Recherches de Biochimie Macromoléculaire, LP 8402 du CNRS, INSERM U.249 Montpellier, France.
Phaneuf
S
S
Derancourt
J
J
Casanova
J
J
Durand-Clement
M
M
le Peuch
C
C
Haiech
J
J
Cavadore
J C
JC
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D001572:Benzofurans; D002118:Calcium / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives*; D008297:Male; D008387:Marine Toxins / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D035964:Oxocins; D010716:Phosphatidylinositols / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012503:Saponins / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D000095702:Polyether Toxins
D000804:Angiotensin II; D001572:Benzofurans; D002118:Calcium; D005456:Fluorescent Dyes; D016257:Fura-2; D008387:Marine Toxins; D035964:Oxocins; D010716:Phosphatidylinositols; D011188:Potassium; D012503:Saponins; C049925:fura-2-am; C020394:maitotoxin; D000095702:Polyether Toxins