Water management is the key to regulating cell volume

Sep 27 2005

Water management is the key to regulating cell volume says Dutch researcher Bas Tomassen. He investigated the uptake and secretion of water by the plasma membrane of animal and human cells.

Cell volume is the outcome of a subtle balance between water uptake and secretion by the cell plasma membrane. A cell can regulate its volume by adjusting the salt concentrations in and around the cell. Exactly how this process works is still not known. Bas Tomassen has identified a number of important mechanisms that play a role in this process.

Increasing the salt concentration in the cell or decreasing the salt concentration around the cell leads to an influx of water. This principle is known as osmosis. Cells activate various channels to remove excess water and salt or osmotically active particles from the cell.

Tomassen studied cells that are highly sensitive for osmotic disruption. He discovered that cells permeable for water can more easily respond to changes in salt concentrations and that volume changes are facilitated by the presence of specific channels that transport water.

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

All organisms in the natural environment are confronted with salt balances in and around their cells. Plants, bacteria and fungi have an extra cell wall that provides the cell with additional protection. Animal cells, such as human cells, do not have this. They have developed other mechanisms, a number of which have been identified by Bas Tomassen.