Water Management In Cells

Cellvolume is the outcome of a subtle balance between water uptake andsecretion by the cell plasma membrane. A cell can regulate its volumeby adjusting the salt concentrations in and around the cell. Exactlyhow this process works is still not known. Bas Tomassen has identifieda number of important mechanisms that play a role in this process.

Increasingthe salt concentration in the cell or decreasing the salt concentrationaround the cell leads to an influx of water. This principle is known asosmosis. Cells activate various channels to remove excess water andsalt or osmotically active particles from the cell.

Tomassenstudied cells that are highly sensitive for osmotic disruption. Hediscovered that cells permeable for water can more easily respond tochanges in salt concentrations and that volume changes are facilitatedby the presence of specific channels that transport water.

Slow organic reaction

In addition to water channels and ion channels, organic particlesplay an important role. If the salt balance is disrupted, so-called'volume-regulated anion channels' are first of all activated. Theseensure that chloride ions leave the cell. Further research revealedthat the efflux of organics only starts one or two minutes later. Thisefflux only takes place if there is a large difference between theintracellular and extracellular salt concentrations. From this theresearcher concluded that the efflux of organics is a second line ofdefence, which is only activated if there are considerable problems.

Allorganisms in the natural environment are confronted with salt balancesin and around their cells. Plants, bacteria and fungi have an extracell wall that provides the cell with additional protection. Animalcells, such as human cells, do not have this. They have developed othermechanisms, a number of which have been identified by Bas Tomassen.

Bas Tomassen's research was funded by NWO.