AJP - Cell Physiology, Vol 254, Issue 1 C20-C26, Copyright © 1988 by American Physiological Society
Ion transport mediated by copolymers composed of polyoxyethylene and polyoxypropylene
T. P. Atkinson, J. O. Bullock, T. F. Smith, R. E. Mullins and R. L. Hunter
Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia 30322.
Block copolymers composed of polyoxyethylene and polyoxypropylene were
found to increase the influx of Na+ and the efflux of K+ from human
erythrocytes. They were, however, ineffective at promoting the transport of
Ca2+. The size of the ion fluxes induced by the copolymers correlated with
their efficacy in stimulating inflammation. These compounds were also found
to induce conductance increases in planar lipid bilayers in a nonvoltage
dependent and nonstepwise manner. In both experimental systems, ion
transport was facilitated only under temperature and ionic-strength
conditions in which the polymers form aggregates in aqueous solution. In
neither system did the concentration dependence of transport activity
exhibit a pronounced cooperativity. These observations are consistent with
the view that aqueous monomers of these surface active agents partition
into the membrane, where they facilitate the conductive movement of
monovalent cations by means of a carrier type mechanism. As a novel class
of ionophores, these substances are of practical interest because they can
be water soluble and are potentially reversible.
