Responses of endothelial cells to hypotonic solutions: lack of regulatory volume decrease.

Hypotonic stress (HTS) activates a Cl- current and releases intracellular Ca2+ in vascular endothelial cells, but there is no co-activation of K(+)-channels. The concomitant increase in cell volume, as assessed from the changes in endothelial cell thickness, is not followed by a regulatory volume decrease (RVD). This lack compensation of the volume increase may be explained by the absence of a concomitant activation of a K+ outward current, resulting in an insufficient efflux of osmolytes during HTS.