Equilibrium and kinetic effects of drugs on the shapes of human erythrocytes.

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Abstract
If the 2 half-layers of a membrane are different in their protein and lipid compositions, they may respond differently to some membrane perturbation (the bilayer couple hypothesis). This hypothesis was applied to explain the changes in shapes of human erythrocytes that are produced by a variety of amphipathic compounds. These compounds are presumed to intercalate by their hydrophobic ends into the lipid portions of the membrane; if the compounds are anions, the binding is preferentially to the outer half of the bilayer; if cations, to the inner half. It is proposed that such preferential binding cases an expansion of one-half-layer relative to the other, with a corresponding change in cell shape. The predicted sidedness of these shape changes is now demonstrated in experiments with methochlorpromazine and 2,4,6-trinitrophenol. Under appropriate nonequilibrium or equilibrium conditions, both of these compounds are shown to be either crenators or cup-formers of the intact erythrocyte, depending upon which side of the membrane they are concentrated in. These results strongly support the bilayer couple hypothesis.