Hypertonic saline resuscitation reduces neutrophil margination by suppressing neutrophil L selectin expression - Discussion

Hypertonic saline (HS) reduces hemorrhage-induced lung injury by suppressing the neutrophil oxidative burst and reducing lung neutrophil influx. This study investigated whether this is caused by the effects of HS on endothelial adhesion molecule expression, the production of chemoattractants in the lung, or a direct effect of HS on neutrophil selectin expression. Methods: BALB/c mice were made to hemorrhage to 40 mm Hg for 1 hour and resuscitated with shed blood and either 4 mL/kg 7.5% HS or two times the shed blood volume of lactated Ringer's solution (LRS). Neutrophil L selectin expression was determined by flow cytometry, total neutrophil counts were obtained by differential staining, and pulmonary endothelial P and E selectin expression was evaluated by immunohistochemistry. Chemoattractants in lung lavages were determined with a modified Boyden chamber migration assay. Results: Chemotactic activity of lavage fluid of HS-treated animals was not significantly different from that of LRS-treated animals, and endothelial P and E selectin expression was not altered by HS resuscitation. Neutrophils of HS-treated animals, however, expressed significantly less L selectin than those of LRS-treated mice. Concomitantly, circulating neutrophil counts of LRS-treated animals were significantly decreased compared with those of HS-treated mice. Conclusion: HS had little effect on endothelial selectin expression and chemoattractant production in the lung. HS significantly decreased neutrophil L selectin expression, however. This suggests that HS resuscitation may reduce lung injury by preventing neutrophil L selectin expression and endothelial adhesion.