Effects of equinatoxin II on isolated guinea pig taenia caeci muscle contractility and intracellular Ca2+. - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Toxicon Année : 2008

Effects of equinatoxin II on isolated guinea pig taenia caeci muscle contractility and intracellular Ca2+.

Résumé

Equinatoxin II (EqT II) is a approximately 20kDa cytotoxic and cytolytic protein isolated from the sea anemone Actinia equina. When injected intravenously to rats the toxin has been reported to produce a rapid cardiorespiratory arrest. In the present study, we show that EqT II increases the tension of spontaneous contractions and induces long-lasting contracture of guinea pig taenia caeci muscle. In taenia caeci, dissociated smooth muscle cells, microspectrofluorometric measurements, using the Ca(2+) indicator fura-2/AM, revealed that the toxin causes a marked increase in intracellular calcium, provided Ca(2+) is present in the external medium. The increase in intracellular Ca(2+) by EqT II was not blocked or diminished by the calcium channel blocker verapamil. Furthermore, pre-treatment of smooth muscle cells with Ca(2+)-ATPase inhibitor thapsigargin, or exposure of the cells to a high K(+) (75 mM) medium did not prevent EqT II-induced intracellular Ca(2+) increases. Replacement of external sodium by sucrose markedly modified the time course of Ca(2+) signals suggesting the involvement of the Na(+)/Ca(2+) exchanger in EqT II action. Our results strongly suggest that EqT II-induced increase in intracellular Ca(2+) and muscle tension are both dependent on the ability of EqT II to insert into the membrane and form pores allowing Ca(2+) influx into the cells. To our knowledge this is the first report showing that EqT II causes contraction and contracture of taenia caeci muscles and increases intracellular Ca(2+) in smooth muscle cells.

Dates et versions

hal-00289853 , version 1 (23-06-2008)

Identifiants

Citer

Robert Frangež, Dusan Suput, Jordi Molgó. Effects of equinatoxin II on isolated guinea pig taenia caeci muscle contractility and intracellular Ca2+.. Toxicon, 2008, 51 (8), pp.1416-23. ⟨10.1016/j.toxicon.2008.03.013⟩. ⟨hal-00289853⟩

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