[Effects of dexamethasone on Ca++-response of bone marrow lymphoblasts in acute leukemia]

The FURA-2/AM fluorescence dye was used to investigate the influence of dexamethasone treatment on the basal and mitogen-mediated levels of free ions of calcium ([Ca++]i) in the lymphoblast cytoplasm from bone marrow of patients suffering acute leukemia. Treatment with dexamethasone in the dose of 2 microM was shown to significantly stimulate the increase of the basal level of [Ca++]i and to inhibit the Ca++ response of cells to concanavalin A (25 micrograms/ml). Inhibition by dexamethasone was more pronounced after 30 min preincubation of lymphoblasts with a glucocorticoid. A phorbol ester--phorbol myristate acetate--reactivated sensitivity to concanavalin A in dexamethasone-treated cells. Determination of lymphoblast Ca(++)-response of dexamethasone treatment may be used for in vitro express testing individual sensitivity to glucocorticoids in treatment of acute leukemia.