Use of the spin label tempamine for measuring the internal viscosity of red blood cells

Abstract

Summary A new spin label-spin broadening system to monitor the intracellular viscosity of red blood cells in isotonic medium at biological pH is described. The spin label 2,2,6,6-tetramethyl piperidine-N-oxyl-4-amine (TEMPAMINE) and the spin broadening agent K 3 Fe(CN) 6 are used for this study. K 3 Fe(CN) 6 does not penetrate red blood cells and at 80 mM completely broadens external aqueous components of the TEMPAMINE signal. Intracellular signal arising from TEMPAMINE is proportional to red cell concentration (hematocrit). TEMPAMINE samples the internal aqueous environment of red blood cells and in conjunction with K 3 Fe(CN) 6 it appears to be very useful for measuring changes which occur in intracellular aqueous spaces.