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Fig. 1. Cartoon illustrating the hypertonic stress response of animal cells.
Exposure to hypertonic media causes rapid water loss and cell shrinkage. Cells
respond to shrinkage by activating regulatory volume increase (RVI) salt
uptake mechanisms. Osmotically obliged water follows salt uptake and cell
volume returns to its original value. Over a period of several hours, cells
replace inorganic ions accumulated during RVI with organic osmolytes.
Accumulation of organic osmolytes is mediated either by energy-dependent
transport from the external medium or by changes in the rates of osmolyte
synthesis and degradation. Hypertonic stress typically increases the
expression of both organic osmolyte transporters and key enzymes involved in
their synthesis. Cells also repair molecular damage including DNA breaks and
protein denaturation induced by the initial cell shrinkage and elevation cell
inorganic ion levels.
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