Herbimycin A Suppresses the Reduction of Gap‐junctional Intercellular Communication Induced by Tumor‐promoting Phorbol Ester in 3T3‐L1 Cells

We have examined the suppressive effect of herbimycin A on the reduction of gap‐junctional Intercellular communication that is induced by a tumor‐promoting phorbol ester in 3T3‐L1 cells. Most cells in growth arrest participated in dye‐coupling, as evaluated by the transfer between cells of a fluorescent dye (Lucifer Yellow CH). Treatment of cells with 0.25 μg/ml herbimycin A slightly enhanced the dye‐coupling. This enhancement required treatment for periods as long as 24 h. Addition of 100 ng/ml 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) caused a rapid reduction of dye‐coupling. However, addition of TPA did not suppress dye‐coupling in cells pretreated for more than 24 h with herbimycin A. Pretreatment of cells for less than 6 h with herbimycin A did not suppress the TPA‐induced reduction of dye‐coupling. These results suggest that herbimycin A suppresses the reduction of gap‐junctional intercellular communication that is induced by TPA through enhancement of the ability of the cells to participate in gap‐junctional intercellular communication