Deficits in elevating membrane potential of rat fibrosarcoma cells after cell contact.

Most cancer cells are known to have lower resting cellular potentials than do their normal counterparts. This study investigates how these potentials establish themselves during growth and cellular contact in tissue culture. Normal quail embryonic fibroblasts and quail fibrosarcoma (QT-35) and normal rat kidney cells and rat fibrosarcoma (from rat fibroblasts chemically transformed by nitroquinoline oxide) were recorded intracellularly using high-impedance micropipets. In high-density high-contact cultures, both quail and rat cancer cells had lower potentials than did normal cells (-20.7 compared to -40.1 mV for quail and -30.7 compared to -61.9 mV for rat). In low-density mitotically synchronous cultures, the rat cells were recorded every 4 hr for 96 hr. Starting at a low density, normal cell membrane potential is maintained at a low level through subsequent cell divisions. Without any additional change in cell density, the potential suddenly elevates to a high level. The membrane potential of cancer cells is by contrast unrelated either to cell density or to time. Cancer cells maintained an intermediate potential from low to very high densities and never elevated their potential to high values. The failure of cancer cells to reach high potentials may be linked to their uncontrolled cell division.