Impaired Erythrocyte Filterability of Spontaneously Hypertensive Rats:

ypertension is 1 of the greatest causes of cardiac events in many countries. In this field, hemorheology has been attracting less attention relative to vascular medicine. However, the deformability of erythrocytes, a major concept in hemorheology, plays a key role in the impaired microcirculation of hypertension.1 The concept of erythrocyte deformability has no strict definition as a physical quantity, so its evaluation depends on measurement techniques, and the relative sensitivities of these techniques are influenced by various factors that comprise deformability. Because the filtration of erythrocytes through artificial narrow pores is relevant to microcirculation in vivo, filtration techniques are the most widely used to assess the physiological deformation of intact erythrocytes in cases where deformation in vivo involves bending. Erythrocyte deformability is quantified as erythrocyte filterability (whole cell deformability) using a gravity-based nickel mesh filtration technique,2–4 because the physiological importance and clinical benefit of this technique are evident.5–7 Recently, we found that disturbed microcirculation in vivo is closely related to impaired erythrocyte filterability,4 as suggested by the Fahraeus–Lindqvist effect.8 Spontaneously hypertensive rats (SHR) are an excellent model of human hypertension.9,10 Erythrocyte deformability influences whole blood viscosity and microvascular resistance at moderate to high shear rates, so it is a fundamental problem in SHR whether erythrocyte deformability is impaired or not. In fact, increased erythrocyte membrane rigidity has been reported in SHR.11–13 Such rheologic abnormalities influence overall blood flow conditions and lead to microvessel occlusion in SHR.14 However, information with respect to erythrocyte deformability is extremely limited.15 In the present study, erythrocyte filterability was investigated during the development and maintenance of hypertension in SHR and age-matched normotensive Wistar-Kyoto rats (WKY), using a nickel mesh filtration technique. H