Spin label study of erythrocyte deformability. III. Further characterizations of electron spin resonance spectral change in shear flow.

It is demonstrated that the change in the spin label ESR spectrum induced by shear flow reflects the whole cell deformation as a function of the cell surface area-to-volume ratio (s/v), the morphology and intracellular viscosity. Since the effect of the change in the membrane mechanical property on the ESR spectrum has been described previously, the spin label ESR spectrum is now shown to contain full information concerning the whole cell deformability which is determined by the major intrinsic and extrinsic properties of the red blood cells. The result of microphotographic observations shows also that the cells in the flow are elongated and aligned approximately along the flow direction to an increasing extent as the cells flow near the surface of the flat channel walls. Thus, the entire observation confirms the view that the ESR spectral difference-shear rate profile is closely related to the elongation ratio shear rate characteristics obtained by other (optical) methods.