Membrane Reserves and Hypotonic Cell Swelling |
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Authors: | Nicolas Groulx Francis Boudreault Sergei N Orlov Ryszard Grygorczyk |
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Institution: | 1. Research Centre, Centre hospitalier de l’Université de Montréal–H?tel-Dieu, 3850 Saint-Urbain, Montréal, Québec, Canada, H2W 1T7 2. Department of Medicine, Université de Montréal, C.P. 6128 Succursale Centre Ville, Montréal, Québec, H3C 3J7, Canada
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Abstract: | To accommodate expanding volume (V) during hyposmotic swelling, animal cells change their shape and increase surface area
(SA) by drawing extra membrane from surface and intracellular reserves. The relative contributions of these processes, sources
and extent of membrane reserves are not well defined. In this study, the SA and V of single substrate-attached A549, 16HBE14o−, CHO and NIH 3T3 cells were evaluated by reconstructing cell three-dimensional topology based on conventional light microscopic
images acquired simultaneously from two perpendicular directions. The size of SA reserves was determined by swelling cells
in extreme 98% hypotonic (∼6 mOsm) solution until membrane rupture; all cell types examined demonstrated surprisingly large
membrane reserves and could increase their SA 3.6 ± 0.2-fold and V 10.7 ± 1.5-fold. Blocking exocytosis (by N-ethylmaleimide or 10°C) reduced SA and V increases of A549 cells to 1.7 ± 0.3-fold and 4.4 ± 0.9-fold, respectively. Interestingly,
blocking exocytosis did not affect SA and V changes during moderate swelling in 50% hypotonicity. Thus, mammalian cells accommodate
moderate (<2-fold) V increases mainly by shape changes and by drawing membrane from preexisting surface reserves, while significant
endomembrane insertion is observed only during extreme swelling. Large membrane reserves may provide a simple mechanism to
maintain membrane tension below the lytic level during various cellular processes or acute mechanical perturbations and may
explain the difficulty in activating mechanogated channels in mammalian cells.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Cell volume Membrane reserve Membrane stretch Three-dimensional cell imaging |
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