Role of Plasma Membrane at Dielectric Relaxations and Intermembrane Interaction in Human Erythrocytes

Dielectric relaxations at 1.4 MHz (& beta;(sp)) and 9 MHz (& gamma;1(sp)) on the erythrocyte spectrin network were studied by dielectric spectroscopy using dense suspensions of erythrocytes and erythrocyte ghost membranes, subjected to extraction with up to 0.2% volume Triton-X-100. The step-wise extraction of up to 60% of membrane lipids preserved & gamma;1(sp) and gradually removed & beta;(sp)-relaxation. On increasing the concentration up to 100 mM of NaCl at either side of erythrocyte plasma membranes, the & beta;(sp)-relaxation was linearly enhanced, while the strength of & gamma;1(sp)-relaxation remained unchanged. In media with NaCl between 100 and 150 mM & beta;(sp)-relaxation became slightly inhibited, while & gamma;1(sp)-relaxation almost disappeared, possibly due to the decreased electrostatic repulsion allowing erythrocytes to come into closer contact. When these media contained, at concentrations 10-30 mg/mL dextran (MW 7 kDa), polyethylene glycol or polyvinylpyrrolidone (40 kDa), or albumin or homologous plasma with equivalent concentration of albumin, the & gamma;1(sp)-relaxation was about tenfold enhanced, while & beta;(sp)-relaxation was strengthened or preserved. The results suggest the Maxwell-Vagner accumulation of ions on the lipid bilayer as an energy source for & beta;(sp)-relaxation. While & beta;(sp)-relaxation appears sensitive to erythrocyte membrane deformability, & gamma;1(sp)-relaxation could be a sensitive marker for the inter-membrane interactions between erythrocytes.

Automated summary

Dielectric relaxations were studied on the erythrocyte spectrin network using dielectric spectroscopy. The extraction of membrane lipids preserved γ1(sp) and removed β(sp)-relaxation. The concentration of NaCl and the presence of certain substances influenced the strength of β(sp)-relaxation and γ1(sp)-relaxation differently.