ENHANCEMENT OF GAP JUNCTIONAL COMMUNICATION AND CONNEXIN43 EXPRESSIONBY THYROID-HORMONES

Cells in tissues coordinate their activity by sharing ions, second mes sengers, and small metabolites through clusters of intercellular chann els called gap junctions. The thyroid hormones 3,3',5-triiodo-L-thyron ine (T-3) and L-thyroxine (T-4) are capable of modulating gap junction al communication (GJC) as are 1,25-dihydroxyvitamin D-3, retinoic acid , and other nuclear receptor ligands. T-3 and T-4 were found to stimul ate GJC in WB-F344 rat liver epithelial cells dose-dependently at conc entrations between 1 nM and 0.1 mu M, assayed by the dye transfer meth od using Lucifer Yellow CH. The stimulation of cell-cell communication was preceded by an increase in connexin43 mRNA levels and was accompa nied by an accumulation of connexin43 protein measurable 2 days after incubation with these compounds. These observations establish a novel role of thyroid hormones in the regulation of gap junctional intercell ular communication via connexin43 gene expression. (C) 1998 Elsevier S cience Inc.