Inhibition of the formation of electrical cell coupling of FL cell by tumor promoters.

The effect of tumor promoters on the formation of electrical cell coupling between human FL cells was investigated by means of a microelectrode technique. In culture medium containing 100 ng/ml of 12-O-tetradecanoyl phorbol-13-acetate (TPA), only 6% of the cells were coupled after 24 hr while more than 90% of the cells were coupled in control medium. The formation of cell coupling was also inhibited by other tumor promoters, phorbol-12,13-didecanoate, ingenol-13, 20-dibenzoate and mezerein, whereas non-promoting derivatives, phorbol and 4 alpha-phorbol-12, 13 didecanoate did not affect cell coupling formation. 7, 12-Dimethylbenz [a] anthracene, benzo [a] pyrene and N-methyl-N'-nitro-N-nitrosoguanidine did not affect the cell coupling. None of the chemicals used changed any electrical properties of the cell membrane, such as membrane potential and membrane resistance, of FL cells. Thus, it appears that TPA and other related tumor promoters inhibit the formation of cell coupling without changing the physiological properties of the membrane significantly.