Hypertonicity-induced alteration of the spectrin network under the erythrocyte membrane (EM) has been proposed as the cause of hypertonic cryohemolysis, however, the exact mechanism is not known. With this in mind we applied thermal dielectroscopy to evaluate the dynamic state of spectrin network of human erythrocytes and isolated EMs as affected by the osmotic pressure of suspension media (10 mM NaCl and varying concentrations of mannit). The method, applied on a heated suspension, detected abrupt changes in the complex impedance, ΔZ* = ΔZ re +jΔZ im , at the spectrin denaturation temperature, T A (49.5 C). The Nyquist plot (-ΔZ im vs ΔZ re ) of these changes indicated two arcs, i.e., two relaxations of the mobile dipoles on intact spectrin network, one centered at 2.5 MHz and the other at 0.3 MHz. Increasing the tonicity from 300 to 500 mOsm both arcs were inhibited. Similar inhibition of the Nyquist plot arcs was obtained by the selective dissociation of spectrin-ankyrin-band 3 bridge of EM. Above 500 mOsm the arcs merged indicating a single relaxation. Both effects of hypertonicity were reversible upon reverting to isotonicity. It is concluded that hypertonicity could lead to a reversible detachment of spectrin skeleton from the integral proteins and inhibition of the segmental motion of spectrin network.

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