Figure 7.

Ursolic acid selectively inhibits the incorporation of amino acids into the cell. (a to d) A549 cells were preincubated with or without ursolic acid (50 μM) or ouabain (10 μM) for 1 h and then incubated with [³H]L-leucine for 2 h in the presence or absence of those two compounds (a); A549 cells were preincubated with or without cycloheximide (10 μM) for 1 h and then incubated with [³H]L-leucine for 2 h in the presence or absence of cycloheximide (b); A549 cells were preincubated with or without ursolic acid (50 μM) or ouabain (10 μM) for 1 h and then incubated with [³H]uridine (c) or [³H]thymidine (d) for 2 h in the presence or absence of those two compounds. Radioactivity incorporated into the cell was separated into acid-soluble supernatants (Sup) and acid-insoluble precipitates (Ppt). Total radioactivity incorporated into the cell (Sup+Ppt; gray bars) as well as radioactivity incorporated into the precipitates (Ppt; filled bars) is shown as means ± SD (n = 3). * P < 0.05 and ** P < 0.01, compared with control; (e) A549 cells were preincubated with various concentrations of ursolic acid for 1 h and then pulse-labeled with [³H]L-serine for 5 min in the presence of ursolic acid. Radioactivity incorporated into the cell was measured. Data points represent means ± SD (n = 3). * P < 0.01, compared with control.