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Vaca, L; Martinez, M; Salvador, C; Farias, JM; Escobar, LI (1999)


TOXICON 37(2):359-370
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The effect of Maitotoxin (MTX) on the calcium-activated chloride current (ICl-Ca) from Xenopus oocytes was studied, applying the two-electrode voltage cramp technique. MTX increased the current amplitude at all the voltages explored and reduced the time to reach the maximum current level (time to peak). At low toxin concentrations (15 pM), both effects were fully reversible. Activation of ICl-Ca by MTX was secondary to the increment in the intracellular Ca2+ concentration induced by this toxin. since incubation of the oocytes with the cell-permeant Ca2+ chelator BAPTA-AM, greatly reduced the effect of MTX on ICl-Ca. Furthermore, external chloride ions removal also diminished the MTX effect on the current, strongly suggesting that the main current activated by MTX is ICI-Ca. Subsequent applications of a fixed toxin concentration after toxin washout resulted in enhanced ICI-Ca, suggesting that the toxin effect potentiates. (C) 1999 Elsevier Science Ltd. All rights reserved.