Affiliations: Department of Physiology and Biophysics, University of Southern California School of Medicine, Los Angeles, CA 90033, USA
Abstract: Using a constant-amplitude (± 1°) oscillatory Couette viscometer (f=0.01–1.0 Hz), we have measured the viscous (η′) and elastic (η″) components of the complex viscosity at 25°C for shape-transformed human RBC suspended in isotonic buffer at 80% hematocrit. Morphology-altering drugs employed were: ECHINOCYTIC AGENT 2,4-dinitrophenol (DNP, 0.1–5 mM); STOMATOCYTIC AGENT chlorpromazine hydrochloride (CPZ, 0.01–0.1 mM). All suspensions exhibited decreasing η′ and η″ with increasing frequency. Compared to biconcave, control RBC suspensions, salient effects of shape transformation included: 1) for DNP, a dose-related elevation of both η′ and η″, with a 850% increase in η′ and a 2500% increase in η″ at 5 mM and the lowest frequency; 2) for CPZ, a dose-related elevation of both η′ and η″, with a 170% increase in η′ and a 280% increase in η″ at 0.1 mM and the lowest frequency; 3) for both DNP and CPZ, the elevations of η′ and η″ were inversely related to frequency. Using 2 mM DNP and various concentrations of CPZ, both η′ and η″ could be returned to control with 0.08 mM CPZ; further increases of CPZ at constant DNP led to elevations of both components. Comparisons of η′ and η″ to steady shear viscometric data indicated that neither a nominal shear rate approach nor a RMS complex viscosity technique was able to completely reconcile these data; a modified Kelvin-Voigt model proved useful in evaluating cellular versus membrane contributions to η″. These results indicate that RBC morphology is an important determinant of the oscillatory behavior of RBC suspensions and suggest the usefulness of the technique for studies of drug-membrane interactions.
