A calcium influx is neither strictly associated with nor necessary for exocytotic membrane fusion in Paramecium cells

摘要: Abstract Exocytosis of trichocysts in Paramecium cells was generally believed to depend on extracellular Ca, since it is accompanied by a Ca influx and not seen the absence Ca. However, short term removal we showed recently that only extrusion secretory contents, but membrane fusion after stimulation with aminoethyldextran (AED), depends We have now extended these studies longer times shown stimulated AED even 1 min at low (≤ 30 nM). At prolonged induced sole In presence AED, trichocyst contents were slowly extruded followed resealing fused membranes, indicating independency endocytotic from (though observed aberrant resealing). Later on, cell death. By using videomicroscopy, further provide first evidence exocytosis necessarily an usual high concentrations (1 mM), local rear end ciliary reversal which triggered influx. conclude neither regularly associated with, nor necessary for, induction exocytotic cells. As source for possible alternative intracellular liberation calcium during exocytosis, analyzed subplasmalemmal alveolar sac system electron spectroscopic imaging found indications redistributions shortly stimulation.