Dependence of erythrocyte deformability on mechanical stress and oxygenation

Abstract

Mechanical properties of erythrocytes are known to be affected by their oxygenation status. Several studies suggested that cytoskeletal rearrangements are carried out in an oxygen dependent manner. The structure of the cytoskeleton determines the mechanical properties of erythrocyte membrane. However, oxygen-dependent mechanical characteristics of erythrocyte are poorly studied whether oxygenated state could alter erythrocyte deformability. In this study, we investigated shear stress induced improvements in erythrocyte deformability through their oxygenation status. Venous blood was collected from male, healthy volunteers (n=10) between 25–50 ages. An informed written consent was obtained from each subject participated in the study according to Declaration of Helsinki. The hematocrit of blood samples adjusted to 0.4 l/l with autologous plasma. Whole blood samples were diluted with polyvinylpyrrolidone (PVP) solution (Mechatronics, Hoorn, Netherlands) with a dilution ratio of 1/200. Blood samples were equilibrated with either ambient air or nitrogen gas for at least 10 minutes at room temperature. Erythrocyte deformability was measured by a laser-assisted optical rotational cell analyzer (LORRCA MaxSis, Mechatronics, Netherlands) applying shear stresses (SS) ranging between 0.3 to 50 Pa. Then, a constant SS of 5, 10 and 20 Pa were applied continuously for 300 seconds and erythrocyte deformability was measured immediately afterwards. Maximal erythrocyte elongation index (EImax) and the SS required for one-half of this maximal deformation (SS1/2) were calculated by using the linear Lineweaver-Burke (LB) model. Deoxygenation of blood samples significantly decreased SS1/2 values both before and after SS applications (p < 0.001). EImax was significantly increased in deoxygenated blood before applying 5 Pa SS (p < 0.05). However, there were no significant differences after continuous SS in oxygenated and deoxygenated blood. Deoxygenation significantly decreased SS1/2/EImax values both before and after SS applications (p < 0.01). SS1/2/EImax values in both oxygenated and deoxygenated blood were significantly decreased after 5 and 10 Pa continuous SS applications although they were not significantly decreased after applying 20 Pa SS. Our study showed for the first time that erythrocyte deformability is improved in deoxygenated conditions in contrast to results presented in previous studies. This deformability improvement may control blood flow and consequently erythrocyte distribution within hypoxic tissues. Our study also demonstrated the relationship of oxygenation-deoxygenation shifts and magnitude of shear stress on erythrocyte deformability.