The day prior to treatment, cells were seeded in a 96-well microplate in 200 ul. of 5% PBS-RPMI medium at a density of 35000 cells per well. Cells were incubated under the same conditions as described for cell maintenance.
Every standard and sample extract was assayed in triplicate. Half the wells of each microplate were pre-treated with ouabain and veratridine corresponding to a final concentration of 1 and 0.1 mM, respectively. Standard solutions and sample extracts were dried