HORMONAL REGULATION OF MEMBRANE PHENOTYPE IN HEPATOMA CELLS *

Glucocorticoids affect the composition and function of the plasma membrane in a variety of cell types.' Incubation of HTC cells, an established line of rat hepatoma cells in tissue culture, with the synthetic glucocorticoid dexamethasone (DEX) alters several membrane properties characteristic of transformed cells, without affecting the growth rate of these cells. Dexamethasone rapidly and reversibly inhibits the active transport of selected amino increases the adhesiveness of the cells to a plastic or glass substrate by a process that requires macromolecular and rapidly and dramatically inhibits the activity of plasminogen activator (PA), a serine protease, which may itself modulate other membrane proper tie^.'^'^ HTC cells provide a favorable experimental system for the investigation of the hormonal regulation of membrane phenotype. The effects of individual hormones, either in isolation or in combination, can be studied in a fashion that is not possible in the intact animal. An established cell line offers the ease of experimental manipulation and stability under a variety of experimental conditions, not usually available in freshly-isolated dissociated cells or in primary cultures of liver cells. The ability to grow HTC cells in suspension culture reduces the need for manipulations such as trypsinization, which can affect transport and other membrane processes. HTC cells have been studied intensively with regard to glucocorticoid receptor function and induction of tyrosine aminotransferase which further enhances their usefulness for our studies. Finally, as discussed in this communication, it is possible to isolate steroid-resistant variant lines of HTC cells allowing the application of both genetic and biochemical techniques to the study of the hormonal regulation of membrane properties in these liver-derived cells.