Neither a nitric oxide donor nor potassium channel blockage inhibit RBC mechanical damage induced by a roller pump

Red blood cells (RBC) are exposed to various levels of shear stresses when they are exposed to artificial flow environments, such as extracorporeal flow circuits and hemodialysis equipment. This mechanical trauma affects RBC and the resulting effect is determined by the magnitude of shear forces and exposure time. It has been previously demonstrated that nitric oxide (NO) donors and potassium channel blockers could prevent the sub-hemolytic damage to RBC, when they are exposed to 120 Pa shear stress in a Couette shearing system. This study aimed at testing the effectiveness of NO donor sodium nitroprussid (SNP, 10⁻⁴ M) and non-specific potassium channel blocker tetraethylammonium (TEA, 10⁻⁷ M) in preventing the mechanical damage to RBC in a simple flow system including a roller pump and a glass capillary of 0.12 cm diameter. RBC suspensions were pumped through the capillary by the roller pump at a flow rate that maintains 200 mmHg hydrostatic pressure at the entrance of the capillary. An aliquot of 10 ml of RBC suspension of 0.4 L/L hematocrit was re-circulated through the capillary for 30 minutes. Plasma hemoglobin concentrations were found to be significantly increased (~7 folds compared to control aliquot which was not pumped through the system) and neither SNP nor TEA prevented this hemolysis. Alternatively, RBC deformability assessed by laser diffraction ektacytometry was not altered after 30 min of pumping and both SNP and TEA had no effect on this parameter. The results of this study indicated that, in contrast with the findings in RBC exposed to a well-defined magnitude of shear stress in a Couette shearing system, the mechanical damage induced by a roller pump could not be prevented by NO donor or potassium channel blocker.