In defense of cell volume?

Most cells react vigorously to perturbations in their fluid volume. Although the responses themselves have been well described, little is known about how the volume stimulus is detected and transduced. The relevance of volume-activated phenomena in vitro to volume homeostasis in vivo is not clear. It can be debated whether cells are truly responding to changes in their volume. Perhaps they are reacting to changes in the concentration of a cytoplasmic constituent. This review calls attention to recent literature bearing on these subjects and concludes that, in most cases, cells are not defending their volume but their concentration of cytosolic macromolecules.