CELLULAR DETERMINANTS OF LOW-SHEAR BLOOD-VISCOSITY

Low-shear viscometry is one of the methods commonly used to estimate t he degree of red blood cell (RBC) aggregation in various bloods and RB C suspensions, However, it has been previously shown that alterations in RBC morphology and mechanical behavior can affect the low-shear app arent viscosity of RBC suspensions; RBC aggregation is also sensitive to these cellular factors, This study used heat treatment (48 degrees C, 5 min), glutaraldehyde (0.005-0.02%) and hydrogen peroxide (1 mM) t o modify cell geometry and deformability, Red blood cell aggregation w as assessed via a Myrenne Aggregometer (''M'' and ''M1'' indexes), RBC suspension viscosity was measured using a Contraves LS-30 viscometer, and RBC shape response to fluid shear stresses (i.e., deformability) was determined by ektacytometry (LORCA system), Our results indicate t hat low-shear apparent viscosity and related indexes may not always re flect changes of RBC aggregation if cellular properties are altered: f or situations where RBC aggregation has been only moderately affected, cellular mechanical factors may be the major determinant of low-shear viscosity, These findings thus imply that in situations which may be a ssociated alterations of RBC geometry and/or deformability, low-shear viscometry should not be the sole measurement technique used to assess RBC aggregation. (C) 1997 Elsevier Science Ltd.