The effects of hyperosmolarity on the viability and function of endothelial cells

Hypertonic solutions have been demonstrated to be efficacious in the treatment of hypovolemic shock. Their continued use when serum osmolarity is elevated may be harmful because they induce cellular dehydration. Because the hyperosmotic tolerance of cells is largely unknown, we determined the effects of increased media osmolarity on in vitro endothelial cell viability and function following periods of normoxia, anoxia, and anoxia with reoxygenation. Bovine aortic endothelial cells were exposed to hypertonic media of 330-570 mOsm/liter for 6-30 hr. Cell viability and function were ascertained utilizing trypan blue exclusion, lactate dehydrogenase (LDH) enzyme release, and cell replating assays. Endothelial cells exposed to media of 460 mOsm/liter demonstrated no significant decrease in the percentage of viable cells (69.81 +/- 6.03 vs 70.64 +/- 4.62% for controls), LDH activity (334.67 +/- 7.91 vs 228.03 +/- 191.28 Berger-Broida U/ml), and replating efficiency (58.27 +/- 42.07 vs 59.10 +/- 5.79%) after 30 hr of normoxic incubation. Hypertonic media up to 570 mOsm/liter did not adversely affect cell viability following a 6-hr anoxic insult. A 6-hr anoxic insult followed by 24 hr of reoxygenation in media of 530 and 570 mOsm/liter resulted in significantly increased viability and replating efficiency compared to 30 hr of normoxia. Our data demonstrate that in vitro endothelial cells tolerate media osmolarity of up to 460 mOsm/liter without apparent decrement in viability or replating efficiency even in adverse conditions of anoxia and reoxygenation. Our data also suggest that exposure to anoxia may induce tolerance of endothelial cells to hyperosmotic media.