Studies on the modulating effects of retinoic acid and retinol acetate using dye transfer and metabolic cooperation...

The effects of retinoic acid and retinol acetate on gap junctional communication were examined in two in vitro tests. Rat liver epithelial cell line IAR 203 was used for dye transfer assays, and hamster lung fibroblast V79 cells were used for metabolic cooperation assays. A reversible dose-dependent inhibition of dye transfer was detected after a 1-hr treatment with retinoic acid or retinol acetate at concentrations ranging from 10 to 50 microM. On the other hand, enhancement of dye transfer was observed after a 24-hr treatment with retinoic acid at 0.1 microM. A dose-dependent inhibition of metabolic cooperation was obtained with retinoic acid at noncytotoxic concentrations ranging from 5 to 50 microM. Retinoids and TPA (1 ng/ml) acted synergistically in their inhibition of cell communication. Thus, the assays appear to be complementary: the dye transfer assay was useful in studying the time course and the reversibility of the inhibition or enhancement of dye transfer, whereas the metabolic cooperation assay was effective in quantifying the inhibitory effect of TPA or retinoids and interactions between them.