The findings are reported in the October 27 issue of Cell. Increased intracellular calcium concentration was visualized as green fluorescence emitted by the calcium sensitive dye fluo-4. The inlet depicts the cells before osmotic stimulation.
Osmotic pressure is the pressure exerted by salts and proteins dissolved in bodily fluids.
When osmotic pressure outside a cell decreases, this leads to an increased tension in a cell's membrane, like the tension in a balloon as it is inflated, a physical stimulus which in turn opens up the channel, allowing ions, among them calcium ions, to pass through, which elicits a cascade of intracellular events. In the case of sensory cells and nerve cells, this is converted into electrical signals to the central nervous system. The scientists cloned VR-OAC from rat, mouse, chicken and human gene libraries. The ion channel was detected in cells from the inner ear, the osmoregulator centers of the brain in the hypothalamus and from cells surrounding whiskers, a rodent's snout hair known to be very sensitive to touch. The presence of VR-OAC in the latter cells suggests that this receptor may also be involved in the sense of touch.