POLYLYSINE INDUCES CHANGES IN MEMBRANE ELECTRICAL-PROPERTIES OF K562 CELLS

The ionic environment of the cell membrane is of extreme importance in maintaining cell integrity and the numerous functions necessary for c ell growth, differentiation, etc., as well as in cell-biomaterial inte ractions. In this study, the effects of polylysine (a basic poly-amino acid with a net positive charge which is often used to coat biomateri als surfaces) on the erythroleukemic K562 cell membrane were investiga ted. In particular, the effects of this polycation were evaluated usin g dielectric relaxation studies in the radiofrequency range with which it is possible to measure both active ionic transport across the cell membrane (membrane conductivity) and the static charge distribution p resent on the cell surface due to the structural components of the cel l membrane (membrane permittivity). The conductivity of the cytosol ca n also be determined. The results demonstrate that while the conductiv ity of the cytosol is not significantly altered, both the conductivity and permittivity of the K562 cell membrane are varied by exposure of these cells to polylysine. These observations indicate that both activ e ionic transport and the type, quantity, or distribution of membrane components such as lipids, proteins, and polysaccharides may also be a ltered. Although the precise mechanisms by which these variations in K 562 cells occur are unknown, it can be hypothesized that changes in th e growth characteristics of these cells may be in part responsible. In particular, as demonstrated by light microscopic examination of K562 cells directly in the culture flasks, the cells in polylysine-coated f lasks do not grow in suspension as do the controls, but rather show an chorage-dependent-like behavior. It is this important change from susp ension to monolayer growth induced by polylysine that may be responsib le for the changes in membrane electrical parameters. (C) 1997 John Wi ley & Sons, Inc.