Regulation of endothelial cell volume during profound hypothermia following hypothermic preconditioning

Hypothermia applied during CV surgery or transplantation is believed to inactivate cellular pump‐leak mechanisms. This allows uptake of Na +1 , Cl −1 and water by the cell, which leads to swelling and organ damage. Osmotic agents in preservation media largely prevent this phenomenon. We hypothesized that hypothermic preconditioning (HPC) at 25°C protects human coronary artery endothelial cells (HCAEC) at 0°C in part by preventing cold‐induced swelling. Confluent cells were preconditioned for 72h or maintained at 37°C, dispersed with trypsin and allowed to reattach for 7 min. Cells were photographed, subjected to 0°C for up to 120h and photographed again without rewarming. Cross‐sectional areas of cells were calculated by digital morphometry and volume calculations assumed that cells were perfect spheres. 0°C caused a progressive increase in cell volume over time (5, 35, 65 or 120% after 24, 48, 72 or 120h). Swelling was unaffected by Cl −1 channel blockers but was reduced 30–40% when Cl −1 was replaced with lactobionate, an impermeant anion. HPC, the iron chelator DFO or the antioxidant GSH protected cells at 0°C and attenuated swelling 25–40%. In conclusion, endothelial cell swelling at 0°C was attributable to Cl −1 diffusion and oxidative stress, while Cl −1 channel inactivation had no effect. The prevention of cold‐induced swelling by HPC was likely due to its attenuation of oxidative stress at 0°C.