Importance of Viscosity Contrast for the Motion of Erythrocytes in Microcapillaries

Abstract

The dynamics and deformation of red blood cells (RBCs) in microcirculation affect the flow resistance and transport properties of whole blood. One of the key properties that can alter RBC dynamics in flow is the contrast λ (or ratio) of viscosities between RBC cytosol and blood plasma. Here, we study the dependence of RBC shape and dynamics on the viscosity contrast in tube flow, using mesoscopic hydrodynamics simulations. State diagrams of different RBC dynamical states, including tumbling cells, parachutes, and tank-treading slippers, are constructed for various viscosity contrasts and wide ranges of flow rates and tube diameters (or RBC confinements). Despite similarities in the classification of RBC behavior for different viscosity contrasts, there are notable differences in the corresponding state diagrams. In particular, the region of parachutes is significantly larger for λ = 1 in comparison to λ = 5. Furthermore, the viscosity contrast strongly affects the tumbling-to-slipper transition, thus modifying the regions of occurrence of these states as a function of flow rate and RBC confinement. Also, an increase in cytosol viscosity leads to a reduction in membrane tension induced by flow stresses. Physical mechanisms that determine these differences in RBC dynamical states as a function of λ are discussed.

Quantitative Analysis of 2D EXSY NMR Spectra of Strongly Coupled Spin Systems in Transmembrane Exchange

“…The 2D EXSY spectra shown in Figure 3 contain sufficient information to constrain all relevant parameters: chemical shifts, J ‐couplings, concentrations of α‐ and β‐glucose (anomerisation is too slow to be observed in this context), apparent rate constants for influx and efflux (which differed for α‐ and β‐anomers), and rotational correlation times. The aqueous suspension medium for RBCs and the haemoglobin‐packed cytoplasm (~340 g L −1 ) are known to have significantly different bulk‐ and micro‐viscosities, which would suggest different rotational correlation times, [35] something that the theory team had independently found to be necessary to obtain a good fit. Although finding a suitable initial guess in the large parameter space (34 parameters for FDG2233 and 19 parameters for FDG33) was laborious, the resulting fits, as shown in Figure 4 , were unambiguous and precise (as inferred from the difference histograms shown in the Supporting Information).…”

Confinement effect on the microcapillary flow and shape of red blood cells

“… 16 The conditions of occurrence of these shapes and the transition between the dynamic shapes critically depend on the RBC properties and the viscosity contrast between RBC cytosol and blood plasma. 21 …”

Alternative View on Blood and Blood Plasma in the Vasculature

“…It is a scale at which the mass flux occurs in the vasculature, and it is, therefore, crucial for living bodies. The role of blood plasma in this regard appears to be still poorly explored in relation to studies on red blood cells (RBCs), although the plasma transmits the shear stress of the flow to RBC membranes forcing their mobility and deformation and, thus, couples the RBC flow with its own flow [1]. The plasma also interacts with the vessel wall and forms a marginal cell-free layer that lubricates the RBC flow [2,3].…”