Detection of receptor-mediated membrane effects of dexamethasone in B16 murine melanoma cell lines by cell partitioning in aqueous two-polymer systems.

Four metastatic variant sublines of the B16 murine melanoma were assayed for glucocorticoid receptors and examined for effects of dexamethasone on surface charge-related partition behaviour in aqueous two-polymer systems, expression of membrane external proteins, and adhesion to growth substratum. BL6 and F10 cells possessed cytosolic glucocorticoid receptors and, on exposure to dexamethasone, showed increased partition in the charged aqueous two-polymer system with high phosphate, but not in non-charged PO4/NaCl buffer system. This suggests that the charged two-polymer system may detect membrane changes that may be receptor-mediated effects of dexamethasone. An increase in expression of certain proteins (p250) was detected in glucocorticoid receptor-positive BL6 and F10 cells but not in the receptor-negative lines. However, other proteins, such as p220, showed an increase in all four cell lines, presumably not receptor-mediated. Dexamethasone produced no detectable changes in the ability of the cells to adhere to plastic substratum.