VACUOLE FORMATION IN MAST CELLS RESPONDING TO OSMOTIC STRESS AND TO F-ACTIN DISASSEMBLY

Authors

  • Anna Koffer,

    Corresponding author
    1. Physiology Department, University College London, University Street, London, WC1E 6JJ, U.K.
      To whom correspondence should be addressed: Tel.: +(44) 020 76796094; Fax: +(44) 020 73876368; E-mail: a.koffer@ucl.ac.uk
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  • Mark Williams,

    1. Physiology Department, University College London, University Street, London, WC1E 6JJ, U.K.
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  • Torben Johansen

    1. Physiology Department, University College London, University Street, London, WC1E 6JJ, U.K.
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To whom correspondence should be addressed: Tel.: +(44) 020 76796094; Fax: +(44) 020 73876368; E-mail: a.koffer@ucl.ac.uk

Abstract

Fluorescent probes were used to visualize the morphology of membranes and of F-actin in rat peritoneal mast cells, exposed to hyperosmotic medium and consequently reversed to isotonicity. Hypertonicity induced cell shrinkage followed by a regulatory volume increase, and cell alkalinization that was sensitive to amiloride, an inhibitor of the Na+/H+ exchanger (NHE), but not to Latrunculin B, an inhibitor of actin polymerization. Using Bodipy-Sphingomyelin, we have observed formation of vacuole-like dilations (VLDs), primarily at or close to the adhesion plane, following the reversal from hyper- to isotonic medium. VLD formation was not inhibited by Latrunculin B or by amiloride. Phalloidin staining has shown that actin filaments do not surround the vacuoles and latrunculin-induced depolymerization of actin has actually promoted vacuole formation, even in isotonic conditions. The results support the idea that a decrease in membrane tension promotes the internalization of the plasma membrane.

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