Amino acids are compatible osmolytes for volume recovery after hypertonic shrinkage in vascular endothelial cells

The response to chronic hypertonic stress has been studied in human endothe lial cells derived from saphenous veins. In complete growth medium the full recovery of cell volume requires several hours and is neither associated w ith an increase in cell K+ nor hindered by bumetanide but depends on an inc reased intracellular pool of amino acids. The highest increase is exhibited by neutral amino acid substrates of transport system A, such as glutamine and proline, and by the anionic amino acid glutamate. Transport system A is markedly stimulated on hypertonic stress, with an increase in activity rou ghly proportional to the extent and the duration of the osmotic shrinkage. Cycloheximide prevents the increase in transport activity of system A and t he recovery of cell volume. It is concluded that human endothelial cells co unteract hypertonic stress through the stimulation of transport system A an d the consequent expansion of the intracellular amino acid pool.