Stabilization of erythrocyte membranes by polyamines.

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Abstract
The effects of putrescine, spermidine and spermine, the 3 physiologic polyamines, on the deformability and mechanical stability of human erythrocyte membranes were studied using a laser diffraction technique. Ghosts resealed with polyamines were subjected to high fluid shear stress in an ektacytometer. All polyamines increased the membrane shear modulus (decreased deformability) in a concentration- and time-dependent manner. The order of effectiveness was spermine > spermidine > putrescine. At 10 .mu.M, spermine appreciably decreased membrane deformability. For the measurement of membrane mechanical stability, resealed ghosts were subjected to constant high shear stress in the ektacytometer and deformability was continuously recorded as the deformable ghosts fragmented into rigid spherical vesicles. Polyamines, especially spermine, caused a noticeable increase in the t1/2 [half-life] for fragmentation. These effects could not be ascribed to proteolysis or Ca2+-induced transglutamination. That the effects of polyamines were specific and not simply due to their positive charge was demonstrated by the finding that Ca2+ and Mg2+ destablized the erythrocyte membrane as evidenced by decreasing the t1/2 for fragmentation. Extracellular polyamines were not effective except under conditions that caused significant accumulation inside the cell. Intracellular physiologic polyamines, especially spermine, apparently decrease erythrocyte membrane deformability and stabilize the membrane skeleton, making it more resistant to fragmentation.