MEMBRANE-CHANGES ASSOCIATED WITH THE TEMPERATURE-SENSITIVE P85(GAG-MOS)-DEPENDENT TRANSFORMATION OF RAT-KIDNEY CELLS AS DETERMINED BY DIELECTROPHORESIS AND ELECTROROTATION

Conventional dielectrophoresis (cDEP) and electrorotation (ROT) measur ements have been used to determine the dielectric properties of a clon e of normal rat kidney cells, designated 6m2, that exhibits a transfor med phenotype at 33 degrees C and a non-transformed phenotype at 39 de grees C. cDEP measurements of the crossover frequencies at which indiv idual 6m2 cells experienced zero cDEP force performed as a function of the conductivity of the suspension medium revealed that, in response to a temperature shift from 33 degrees C to 39 degrees C for 24 h, the mean specific cell membrane capacitance and conductance fell signific antly (P < 0.01) from 42.3 (+/- 1.3) to 30.3 (+/- 2.9) mF/m(2) and 743 (+/- 422) to 567 (+/- 326) S/m(2), respectively. ROT analyses demonst rated a similar reduction for the membrane capacitance from 37.2 (+/- 7.3) to 27.4 (+/- 6.1) mF/m(2), and also showed that accompanying chan ges in the mean internal electrical conductivity and dielectric permit tivity of the cells were insignificant. Scanning electron microscopy w as used to examine the surface morphology of the cells and, in agreeme nt with our previous reports for leukemia cells, the observed membrane capacitance values correlated closely with the morphological complexi ty of the cell membrane surface. The observed changes in the membrane dielectric properties are discussed in terms of their biological signi ficance and their relationship to previously-detected changes in cell surface charge.