title: The role of calcium in the tumor promoter-induced inhibition of gap junctional intercellular communication.
abstract: The effect of several tumor promoters (12-O-tetradecanoyl-phorbol-13-acetate (TPA); 1,1'-(2,2,2-trichloroethylidene)bis[4-chlorobenzene] (DDT); Aroclor1260, and clofibrate) on the inhibition of gap junctional intercellular communication (GJIC) and intracellular calcium concentration ([Ca(2+)](i)) was studied in a cell line consisting of initiated cells (3PC). In addition, the effect of different extracellular calcium concentrations ([Ca(2+)](e)) on the effects of tumor promoters on both GJIC and [Ca(2+)](i) were studied. Agents with GJIC inhibiting capacity increased [Ca(2+)](i). However, the increase of [Ca(2+)](i) did not (always) precede GJIC inhibition. The effect of tumor promoters on GJIC were similar under low (0.05 mM) and high (1.20 mM) Ca(2+)(e) conditions, while different effects on [Ca(2+)](i) were found. These results suggest that tumor promoters can inhibit GJIC and change [Ca(2+)](i), but that there is no direct relationship between these two processes.
authors.affiliation: Agrotechnological Research Institute (ATO-DLO), Department of Food Safety, P.O.Box 17, 6700 AA Wageningen, The Netherlands; Agricultural University Wageningen, Department of Toxicology, Tuinlaan 5, 6703 HE Wageningen, The Netherlands.
authors.forename: L A
authors.initials: LA
authors.lastname: Jansen
authors.forename: T
authors.initials: T
authors.lastname: de Vrije
authors.forename: J H
authors.initials: JH
authors.lastname: Koeman
authors.forename: W M
authors.initials: WM
authors.lastname: Jongen