Veratridine-mediated Ca2+ dynamics and exocytosis in Paramecium cells

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BLANCHARD, Marie-Pierre, Norbert KLAUKE, Sabine ZITZMANN, Helmut PLATTNER, 1999. Veratridine-mediated Ca2+ dynamics and exocytosis in Paramecium cells. In: Journal of Membrane Biology. 169, pp. 155-165. ISSN 0022-2631. eISSN 1432-1424

@article{Blanchard1999Verat-6811, title={Veratridine-mediated Ca2+ dynamics and exocytosis in Paramecium cells}, year={1999}, volume={169}, issn={0022-2631}, journal={Journal of Membrane Biology}, pages={155--165}, author={Blanchard, Marie-Pierre and Klauke, Norbert and Zitzmann, Sabine and Plattner, Helmut} }

Zitzmann, Sabine Blanchard, Marie-Pierre 2011-03-24T17:29:21Z application/pdf 2011-03-24T17:29:21Z 1999 First publ. in: Journal of Membrane Biology 169 (1999), pp. 155-165 Zitzmann, Sabine Blanchard, Marie-Pierre Klauke, Norbert deposit-license Plattner, Helmut We analyzed [Ca2+]i transients in Paramecium cells in response to veratridine for which we had previously established an agonist effect for trichocyst exocytosis (Erxleben & Plattner, 1994. J. Cell Biol. 127:935 945; Plattner et al., 1994. J. Membrane Biol. 158:197 208). Wild-type cells (7S), nondischarge strain nd9 28°C and trichocyst-free strain trichless (tl), respectively, displayed similar, though somewhat diverging time course and plateau values of [Ca2+]i transients with moderate [Ca2+]o in the culture/assay fluid (50 mM<br />or 1 mM). In 7S cells which are representative for a normal reaction, at [Ca2+]o = 30 nM (c.f. [Ca2+]i rest 4 = ~50 to 100 nM), veratridine produced only a small cortical [Ca2+]i transient. This increased in size and spatial distribution at [Ca2+]o = 50 mM of 1 mM. Interestingly with unusually high yet nontoxic [Ca2+]o = 10 mM, [Ca2+]i transients were much delayed and also reduced, as is trichocyst exocytosis. We interpret our results as follows. (i) With [Ca2+]o = 30 nM, the restricted residual response observed is due to Ca2+ mobilization from subplasmalemmal stores. (ii) With moderate [Ca2+]o = 50 mM to 1 mM, the established membrane labilizing effect of veratridine may activate not only subplasmalemmal stores but also Ca2+o influx from the medium via so far unidentified (anteriorly enriched) channels. Visibility of these phenomena is best in tl cells, where free docking sites allow for rapid Ca2+ spread, and least in 7S cells, whose perfectly assembled docking sites may consume a large part of the [Ca2+]i increase. (iii) With unusually high [Ca2+]o, mobilization of cortical stores and/or Ca2+o influx may be impeded by the known membrane stabilizing effect of Ca2+o counteracting the labilizing/channel activating effect of veratridine. (iv) We show these effects to be reversible, and, hence, not to be toxic side-effects, as confirmed by retention of injected calcein.<br />(v) Finally, Mn2+ entry during veratridine stimulation, documented by Fura-2 fluorescence quenching, may indicate activation of unspecific Me2+ channels by veratridine. Our data have some bearing on analysis of other cells, notably neurons, whose response to veratridine is of particular and continous interest. eng Plattner, Helmut Veratridine-mediated Ca2+ dynamics and exocytosis in Paramecium cells Klauke, Norbert

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