Alteration of calcium transport by tumor promoters, 12-O-tetradecanoyl phorbol-13-acetate and p,p'-dichlorodiphenyltrichloroethane, in the Chinese hamster V79 fibroblast cell line.

Effects of two tumor promoters, 12-O-tetradecanoyl phorbol-13-acetate (TPA) and p,p'-dichlorodiphenyltrichloroethane (DDT), on cellular calcium regulatory mechanisms were studied by using the Chinese hamster V79 fibroblast cell line. Both compounds at concentrations known to inhibit cell-cell communication, increased the cellular 45Ca2+ uptake and inhibited its efflux. DDT inhibited Ca,Mg-ATPase of the plasma membrane, while TPA stimulated cellular uptake of Ca2+. A working hypothesis has been proposed that the increase in intracellular concentration of Ca2+ by the action of these chemicals directly results in the closure of the central opening of the gap junction, and thereby causing a cessation of gap junction-mediated intercellular communication.