Susceptibility of density

Accumulating evidence demonstrates that subhaemolytic mechanical stresses, typical of circulatory support, induce physical and biochemical changes to red blood cells. It remains unclear, however, whether cell age affects susceptibility to these mechanical forces. This study thus examined the sensitivity of density-fractionated red blood cells to sublethal mechanical stresses. Red blood cells were isolated and washed twice, with the least and most dense fractions being obtained following centrifugation (1500g？×？5？min). Red blood cell deformability was determined across an osmotic gradient and a range of shear stresses (0.3–50？Pa). Cell deformability was also quantified before and after 300？s exposure to shear stresses known to decrease (64？Pa) or increase (10？Pa) red blood cell deformability. The time course of accumulated sublethal damage that occurred during exposure to 64？Pa was also examined. Dense red blood cells exhibited decreased capacity to deform when compared with less dense cells. Cellular response to mechanical stimuli was similar in trend for all red blood cells, independent of density; however, the magnitude of impairment in cell deformability was exacerbated in dense cells. Moreover, the rate of impairment in cellular deformability, induced by 64？Pa, was more rapid for dense cells. Relative improvement in red blood cell deformability, due to low-shear conditioning (10？Pa), was consistent for both cell populations. Red blood cell populations respond differently to mechanical stimuli: older (more dense) cells are highly susceptible to sublethal mechanical trauma, while cell age (density) does not appear to alter the magnitude of improved cell deformability following low-shear conditioning